Tanya - I was at a day long work thing yesterday and I'm sorry I didn't jump on this thread earlier. I want to offer you my support. And, since I'm a coach by living, I also want to offer you the option to talk by phone if you'd like (obviously completely free of charge) if you think that will help. However, in this thread, I think the best way I know to offer support is to share my story and those of others in similar positions to yours.
Firstly, I have been through this personally myself. All the words you said people say to you, they said to me. Before starting my second career I was in the sciences - both grad and under grad school. And now one of my best friends is a molecular biologist and one of my clients is a PI.
Let me start with my friends: the molecular biologist still does some work on the bench and she does dress down but not shabby for them and is quite polished in non bench situations. Her style isn't as dramatic as mine but she's sophisticated, polished, and well put together. The PI is one of the best dressed women I know. She is always in a new outfit, super well put together, uses lots of color and color combinations, makeup, and jewellery, high heels, and even paints her fingernails. She is the youngest PI in her facility so it's not that she's super established in her career yet. One caveat, it does help that the director of her lab is also female and is generally well put together though not on the same planet as her.
As for my story - when I first started working, I was the only technical woman. After about 5 years of my career, due to a comment that a colleague made (well intentioned), I had a huge a-ha moment. I realized that I'd just spent 5 years of my life trying to be a man. I dressed, behaved, talked like them to the point that I had really assimilated into their culture but that I hadn't distinguished myself from them. And, the fact is, that I'm *not* a man. No matter how hard I try, I can never be one of them. That's when I vowed to be authentic and true to myself no matter the cost. On the dressing front, I first started by finding a small piece here or there, usually an accessory that was "me" - brightly colored, unique piece, dramatic. And I started getting some small compliments on the earrings or shoes I wore. On the flip side I had a boss who once told me at a meeting "those are the ugliest shoes I've ever seen" - and these would be a pair that all of you would consider attractive! I just chose to ignore his comment and keep wearing those shoes. The perfect comeback that I thought of later that night was: "there's no accounting for bad taste, is there?". Slowly then, I started buying signature clothing items that stood out and called out the fact that I was different and a woman (I *never* wore revealing clothes though). After a while, I had another boss comment that I was the best dressed person on the team - and in a nice way. By this time I had already established my credibility through the *results* of my work. So I did have the luxury of spending some crediblity dollars on being myself. If I had to do it over again though I would start being me from day one so people could get used to that and not wasted 5 years of my life miserable trying to channel the opposite gender!
Even after all that, I was still acutely conscious of the time wasting comments you mention. I used to act in theater and found myself sneaking out for rehearsal and then working late at night afterwards. Even though I put in more hours and results than the rest of them combined sometimes, I wasn't comfortable telling them about my theater work for fear of exactly what you're saying. Till after a couple of years when I realized I was doing the same thing and made a fresh pledge to be authentic. And guess what - it all worked out fine. The promotions still kept coming and I was now able to fully "come out" so to speak and live life large and authentically.
Interestingly enough, as an executive coach, I work with many extremely senior men and women and my experience is that most people struggle with some flavor of this issue - even the men! It may not be in how they dress, but in some way shape or form, so many people are looking for ways to fit in, gain more credibility, gain approval, and acceptance. It seems to be part of what makes us human. And those who are most successful are the ones who have figured out how to take a stand that honors themselves - while there might be short term pain, they have gained the long term respect of their colleagues.
I'm sorry I've written on and on but this is a topic that I have *lived* all my life and a place where I believe in helping others. Net net, I would say: find ways to be yourself underneath it all - and you choose (instead of them telling you) what you want to show and not show of yourself. Find at least one small way in which to express who you are and then slowly build up on it. One sophisticated, classy, and authentic step at a time. It may not seem like it at the time, but if you know what you're doing technically, you will shine through and people will learn to accept you for who you are over the long haul once you have your foot in the door.