Michelle, I've just read both this post and your experience at Christmas with your mum. I'm very sorry that you have felt and currently feel so distraught.
I wanted to let you know that I, too, understand how one word from a parent can sometimes cause hurt to the psyche on a deep level that it is hard to recover from. My own experience has been that sometimes however much she loves us, a mother sometimes has an extra special ability to make us feel like an incompetent child, even when we are a fully functioning and totally capable adult.
From how you express yourself on this forum, I must say that I get a strong impression that you are rapidly reaching a point where you have confidence in the way you choose to dress and style your appearance. As such, I'm going to suggest you now should consider being very brave and start to very gently and lovingly assert yourself to your mother that you are now a woman who has her own ideas about her style and presentation.
I understand how difficult attending an emotional event (such as a wedding) can be when there are additional factors present that have the potential to turn what should be a pleasant experience into an absolute emotional nightmare!
With my brother's wedding I'm incredibly stressed because my father has a new girlfriend who he is bringing to the wedding. Let's just say the introduction between us (and many other things that have occured since then) has meant that the relationship between my previously close father and I is incredibly strained.
I have not seen my family for nearly twelve months and my father's side of the family since my mother's funeral three years ago. Essentially, this wedding is the first time I will be thrust into a pool of family dynamics which is quite possibly not going to be pleasant.
In response to my very intense stress, I have decided to be emotionally proactive in order to ensure I am not emotionally vulnerable on this day. Being proactive also means that I can ensure my gorgeous brother and his beautiful new wife have a special day that is not marred by conflict. As such, I have prepared myself to say two sentences if the worst should (and likely will) eventuate at the wedding: "Dad is very happy." If pressed (or attacked) I have decided to say "All that matters is Dad's happiness, my thoughts and opinions are irrelevant." (Smile and then change topic of conversation.)
This approach gives me that capacity to handle myself in a mature, dignified way, whilst still staying true to myself. I believe these responses will not cause additional conflict either, which is just as important. Michelle, take a deep breath because I'm going to be brutally blunt here for a moment:
I think that given your past experiences, you should mentally prepare yourself that your mother will not like your outfit. Further, I think you should expect her to repeatedly make the type of comments you've described in your post. I'm sad to say, this may be her programming (to be inclined toward the negative rather than the positive) and it can be a hard habit to break.
I'm suggesting you come up with some simple, dignified, one sentence comments that you can say in reply or to deflect any negative comments. Such as "I'm sorry you feel that way mum, I actually really like my outfit." Then practice smiling nicely. NOTE: It is important you stop there Michelle, no other words of defence or explanation.
Any more explanation turns it back into the adult-child dynamic. Leave the conversation hanging if necessary and break the tension with "Is Uncle John here, I haven't talked to him in ages, lets go say hi!" (happy voice). If she makes comments about your weight you could say something like "Thank you for your concern about my health mum." (Once again smile and deflect.) You are a smart woman, I know you could come up with far more articulate and appropriate responses!
Michelle, I'm not recommending you say these sentences in a rude or disrespectful way - she is your mother and is entitled to her opinion afterall! You need to practice saying these comments as an assertive statement in a kind and appropriate manner. And yes, I would add that if you have to repeat *exactly* the same sentence five times to various comments which all have that same degree of angst, then say it five times! (Think of it like an experiment and training - stimulus/response; stimulus/response. She will get the message eventually!)
Michelle, I really hope that maybe something I've written is food for thought. Even if it isn't, hopefully just knowing you are not alone in dealing with an emotional rollercoaster makes you feel a little better and less alone.
I really hope you can not let this concern stop you from having a wonderful time at the weddings. Please let us know how the wedding goes (and don't forget to post pictures too)!