I want to thank everyone for the support and thoughtful responses, and especially to Suz for sharing your own experiences.
Several of you have made the recommendation of removing myself from the group text- that's not an option for me right now, unfortunately.

Well— there’s a lot going on in these relationships, and a lot that can go down the tubes. And a whole lot of the responsibility goes to both of the ex’s- i
and stuff involving the ex’s children is fraught. So wishing you patience and wisdom and hoping things improve over time. I am not a counselor at all but I can see why counseling can be necessary sometimes because of all the landmines.
Text is a whole “ new” ( not so new now) issue for communication- benefits and burdens.
I do think it’s quite hard to tell others a start and stop timeframe of acceptable text time— because that would be all over the map for all one’s different family and friends. And sometimes it might vary as to day of week. Dinner time, bedtime, all that. Plus, sometimes needs or wants to manage some text before actually being at work, so that can be a short window, too early vs wait until 6 pm. And all that is easier the better the relationship,
And boundaries- that’s a good idea , but crosses over into the lack of control we have over others’ behavior, vs our reactions, as to how to actually “ set” a boundary that lessens frustrations instead of causing more. It’s very hard on you if you are trying to do boundary- setting that might need to come from your fiancé. Or which boundaries are the most important to focus on.
So I also liked the advice about answering a bit later, but noticed you said something about several hours later, the text hadn’t answered - would you wanted to have it answered sooner, but just not so early?
Also agree with not too much detail in replies, instructions.
Another thing is how actually to communicate— text and e- mail are always tempting, first just because responding in kind- text to text etc- and it’s less in-person, sometimes one feels like having a record, and for me I might avoid saying something I didn’t intend haha! But for that reason also it’s more “ hard” than a verbal/ phone call, and usually harder to include warmth or humor and also IS more permanent, whereas spoken words, assuming not harsh, dissipate a bit. So talking “ live” has some advantages for dealing with some topics and some people. I have sometimes made myself written talking points & scripted sentences for difficult phone calls when I felt the spoken word would actually be more effective ( in a variety of senses if the word) if I could stay on script! When possible I try to have “ good” or ordinary/ pleasant topic predominate and then add request for some accommodation. I might even text, hey, I’ll call you on phone in a bit.

Sending sympathy/ empathy as have had to deal with “ difficult people” at times myself.

Wow, I sympathize. I dealt with an ex-husbands wife and communications were often challenging and yet necessary because of children...and that was before texting! I'm familiar with the ways someone can try to remote control your life.

I'm all for boundaries and courtesy when considering time of texting, same as we would do with a telephone call. I do receive texts from people in other time zones very early in the am, but I am asleep with my phone on silent, and they know that. Barring an emergency, I will answer at a later more convenient time, which they also know. If someone isn't trying to control you, they really don't mind.

I think MsMary may be right here Kris, you are unable to control the time she messages or her passive aggressiveness but you are able set your own boundaries on if and when you respond to her message.

Personally, I have the volume turned on for phonecalls (for emergencies) but turned off for all other apps on my mobile. I have friends and family who work Nightshift who will send a message when it's convenient to them (often before they go to bed in the morning) and I will respond when it's convenient to me.

CS, I am so sorry that you are dealing with this when you already have more than enough stress in your plate. I have no experience to offer, but just echoing the notion that you are totally entitled to set your own firm boundaries with no explanation required. It sounds like this woman enjoys stirring up controversy, so the best way to 'win' (not the right word but ykwim) is to not engage as much as possible.

And I also think it's fair for you to expect your fiance to step up here and set firm boundaries himself. I can imagine a certain personality type sort of trying to pacify rather than engage in the name of peace ... If she's a bit of a bully and he is like this (my DH would probably be so I don't mean this judgementally), then he may have to learn to draw firm lines and cope with the backlash. In any case, I don't know if that makes sense but what I'm trying to say is, do what's yours to do, but don't take on his work or hers! You've got enough on your plate and they ultimately need to sort themselves.
Hugs to you xx

You helped me through a job interview; when they mentioned that help is available for noobs, but you might have to wait, the strategy of sending just a question mark was at the front of my brain, so I laughed and said I wouldn’t do that. I think that scored me some points, so high five!

Not that I’ve ever made a long-term relationship work, but I think my tendency would be to calmly step in and gently protect, because the man in the middle is likely to be more wounded by the attacks because of their joint past history. Stepping back sounds great, but festering in her own juices clearly just gets her more upset. Unfrumped’s suggestion of warmth might work there—starting interactions with a positive about the kids or something she’s done with/for them. One thing to keep in mind might be the advice for couples arguing: if “you” or “I” win, then “we” loose. Both need to be on the side of “us”. In this case, the “winner” needs to be the kids, not any of the step/parents, in mho.

I wish there was a way to set ringer volumes for different callers. I keep mine on low or off, and usually feel the buzzing. When I misplace it though, it sure would be nice if my son’s ring would be loud!

The early text isn't an on going issue and I have things managed on my phone.

It's a nice idea to say "Let him deal with it", but the reality of that was that she bullied him into things he didn't really agree with, or in his trauma response he would forget we had something else we had committed to already, or she would pepper him with insults instead of confirming plans and we would be caught off guard by what she thought we had agreed to. He's asked me to be a part of this to support him in getting to a place where they can communicate effectively, and I have agreed to it. For the most part, it's better than it was. Sometimes, we have these hiccups. Then it continues improving. She is starting to realize the things she says are not ok- and that's huge.
She's more than a little bit of a bully. He believes she has borderline personality disorder, and I don't disagree. He's more than a little traumatized by his relationship with her. We're working through it all.

Another high five!

I hope this doesn't sound like I'm infantilising your fiance because that isn't my intention at all. It just appears that by placing rules around how you engage with his ex you may be modelling boundary setting in an approachable way for your fiance given his trauma.

A 21 year-old is a “child”? I would hope that they would be responsible for their own hair at this age, unless disabled. Are any of the children actually children? Just saying that the immediacy of needing communication replies is very different for a 21 year old, or even 17 year old than an 8 year old…

I also have “Do not Disturb” or now it is called “Sleep” on my iPhone, on until after 8:30 AM, from 10 PM. That being said, I have my daughters and sister, who takes care of my mother, on the “allowed notifications “ list, which are the only calls or texts that would be let through, in case of emergency.

I really feel for you. There is not much control for you in this situation, other than your reaction. Your best option would seem to be stepping back and not engaging, leaving that to your husband, but you will probably be simmering inside. So go punch a punching bag, or whatever, and imagine her face, lol!