Role models. What do we know?

As women in mathematics, we are role models as soon as (potential) students know that we are there. But is that enough to attract students and to keep them in the field? Do female students have to meet us as lecturers, as supervisors,... How much contact does it take?
There is a lot of literature on the subject, and in countries where we are very few, it is important not to have to take part in every campaign, meeting with students,...