The Ajah's tend to "guide/recruit" I don't think the Accepted really make this choice themselves, except under extremely odd circumstances such as Pevara. Point being it seems logical that the Blue, political as they are, would take great interest in young and powerful women, possibly beginning the recruitment process from her first days in the Tower, or at the very least once they realized she wasn't a shoe-in for another Ajah (i.e. painfully logical etc...).

Certainly there are women that are clearly headed to a specific Ajah based only on personality (i.e. everyone knows a White's mentality when they meet her), but I'd say that most of the time Novices and Accepted are more middle of the road in terms of personality, who would have guessed Faolain would choose the Blue for instance? For a woman like her the Blue may well have latched onto her sense of justice and her passion, and used that to guide her away from what seemingly should have been a choice for the Red. They likely would have ignored this part of her and let her gravitate toward the Red had she been weak in the Power.