I didn't read the whole thing, but like always there seems to be a lot of morons on both sites.
I just want to point one thing out: Yes it matters how she was dressed and also her body language.
I don't know about this particular Meetup, I wasn't there. So maybe what I say, doesn't apply here.
If you walk in a bad neighborhood, dressed all slutty, than you don't have the right to tell everybody what pigs are men, when somebody asks you how much "it" costs.
If you sit in a meeting with a dirty shirt and everybody else is dressed business-style, you can't complain, if they don't take you seriously.
If you are in a meeting and your body language is all flirty(e.g. winking at men) than you can't complain, if they are going to hit on you.
Every human being takes part in how it is treated by other human beings.
You are entitled to your opinion when you see someone, but you are not entitled to sexually harass a women just because she's "dressing slutty", especially since it's a super fucking subjective quantifier.
Also, you're a complete moron if you stop at a person's appearance in a meeting, some of the most important stuff I've had to say was the morning after I spent a straight night working on something. You better be god damned sure what I have to say will rock your world if I come in a meeting with a coffee stain on my shirt and my sleeves rolled up.