A few points...
Yes, traditionally "feminine" women get a lot of flak, and yes, it doesn't surprise me to hear that young women can be turned off by feminine STEM role models. The women who have paved the way in STEM fields have often done so by becoming "one of the guys": jeans and cargo pants, ThinkGeek shirts, hoodies, duct tape wallets, etc. And that's all just fine. I did that myself for years. But when a manager at work pulled me aside at one point and suggested I start dressing more professionally to reflect the roles I'd taken on, and I thus started dressing in trousers, blouses, and heels, I was surprised at the comments I got from people -- always "joking", of course, but still negative and problematic in aggregate . "You don't look like an engineer!" "How can you be our cool geek girl if you're wearing pearls?" etc etc etc. So now that the stereotype of engineers is not just "geeky men in free Linux distro tshirts" but is moving toward "geeky men and women in free Linux distro tshirts", we've created a new stereotype that many young women who are traditionally feminine may not fit. On the other hand, the young women who are maybe attracted to STEM fields because they are the ThinkGeek shirt-wearing geeks will be turned off if suddenly all the STEM outreach for women changes to "Attractive feminine women in heels" -- that might be exactly the kind of girl they feel bullied or intimidated by in school, and the last thing they want to do is go into a field that is advertised as being for the same women they're trying to avoid. The problem is the extreme generalizations one way or another about young women and their interests, whether it's "they're not interested in STEM at all" or "they'll only be interested if it can be about sewing and lipstick". Surprise, women aren't all the same! And we need to find ways to attract *all* of them, not just a specific type. So there needs to be space for outreach to appeal to different types of women without criticism.
To address another point, from the perspective of someone who gets to be a (literal) poster child and role model for women in STEM, it's frankly exhausting. And I'm early in my career; I can't even imagine with the Marissa Mayer, Helen Greiner, etc types have had to deal with. It's an incredibly rewarding thing, to get to talk with younger students and get them excited about the things I'm passionate about, don't get me wrong. It's something I love to do. But when you're the go-to token Tech Woman, you start having to turn down offers because your day job (and FIRST!) keep you so busy, and not only that, you feel as though you're under a lot of scrutiny. Once you have a reputation as a Woman in Tech you start worrying about how your own decisions affect that. What if I get into project management and out of the day-to-day technical stuff, am I selling out and not being "STEM" enough? Is that too stereotypical of women? What if I move somewhere else because of my partner's job; am I going to disappoint people who expect me to be more focused on my career, even if I can find ways to keep it going in the new place? I'm still a few years away from starting a family, but I'm already panicking about what I'm "supposed" to do about maternity leave (and
articles like this really don't help -- there doesn't seem to be any right answer that doesn't inspire judgement and criticism).
People were responding to another poster telling her not to worry or go crazy thinking about this stuff. But I completely understand her and I do it too. When you're so often the only woman available as a role model, you feel a lot of pressure to make sure you're doing it "right". And to those of us who didn't necessarily have female role models doing exactly what we wanted to do, we feel it is incumbent upon us to manage to show everyone else that "it" can be done, whatever "it" is for us -- having the high-profile job, being heavily involved in some other hobby or organization, being feminine while still being a well-respected engineer, successfully managing a family, whatever. Whether or not that's sane or reasonable to feel is beside the point; the point is that many of us DO feel this pressure and it's affecting what and how we're able to contribute to these outreach efforts.
So why can't you get female engineers to come mentor, to come speak, to come be role models? Because they're probably already doing it a whole lot, and whether it's because of schedule or because of feeling a little drained, they may just not be able to do it yet another weekend.
What's the solution? Well, if I knew that, I'd be a lot less stressed about this. But I wonder if maybe (perhaps paradoxically) the answer is to get *more* women, at the same time, in to mentor/speak/etc at the same time as multiple men. Make it incidental that there are female role models present; don't make it the focus. It takes pressure off them if they're not told PLEASE COME REPRESENT HALF THE POPULATION AND TELL OUR FEMALE STUDENTS HOW TO SUCCEED.
Have you ever noticed that half our judges at the Boston Regional are female? That's intentional. But we don't point it out. We don't make a big deal of it. We don't recruit judges of either sex, or of any ethnic or racial minority, or of any age, or of any particular occupation, saying "Please come be our token [whatever] judge!" We just put together a good, interesting group of people who represent different races, different sexes, different ages, different levels of nerdiness or femininity or fashion-consciousness, and different ways to engage with STEM in real life. And we let the students decide who among that group can be the most meaningful role model(s) for them, and hope that we've done a good thing to provide so many different kinds of inspiration.
I don't mean to denigrate the efforts of STEM outreach that focuses on female role models. I think that's good and that it can work. But people have pointed out where it doesn't seem to be working and the trouble they have finding women willing to help out, and I wanted to address some of the reasons I think that is the case.