The problem with recruiting female engineers really comes down to numbers.
According to some statistics I've heard before, only 13% of engineers are female, and the percentage can be worse when you look at specific engineering fields.
My experience at companies I've worked for shows that very few people want to dedicate the time and energy to mentor a team. Maybe 1/1000 people. Now, that's fine when you look at trying to recruit someone (non gender specific) to mentor your team, as there are a lot of comeanies out there, and hundreds of thousands of engineers you could draw from. When you start applying filters to your recruitment criteria (must be female, or must be a specific type of engineer, etc), your pool of potential recruits rapidly decreases, and your left looking for a specific needle in a haystack full of needles that aren't quite right.
My team doesn't actively recruit female mentors, despite being an all girls team from an all girls school. We recruit mentors, and those mentors ensure there's a gender-neutral attitude in everything we do. the female mentors we have fall into three categories: parents, teachers, and returning former students. It just happened to work out that way.
For those female student here, I want to ask - which is more important to you, having a female mentor to look up to, or having your mentor (regardless of gender) show confidence, support, and respect for you? At the end of the day, that's all us poor males can really do to help you grow!