Let her know how much she means to you (not in an “even if you’re single!” kind of way.) Encourage her interests. Don’t let conversation veer to guys too much, even if you’re giving her advice to ignore them (few actually heed the “It will happen when you stop thinking about it” mantra). Join her in a new passion. Lead by non-guy-obsessed example. Boost her confidence in subtle ways. And if it’s really severe, of course, your role might be to encourage her to get a professional to join the cause.