One of my best friends chose to "play for the other field" after being hurt too many times by guys. Sometimes it takes a few heartbreaks to realize that you actually need someone that can understand the way you think, and with girls who could possibly know you better than another girl?
Milicent does have a point though, it's the big thing in school to be bisexual or gay just for attention, and you can usually pick out those people that aren't 100 percent real. But there are those who are actually gay and are proud to admit it, though some obusively claim that they too are only out for attention.
In answer to your question, i say yes, some girls do choose to change their sexuality due to hurtful men in their lives