I've observed this phenomena for 20+ years, there is a certain percentage of women who are interested in other women sexually. The difference between now and then is a lot of sexual restrictions that society placed on women have been lifted. Now days its acceptable to be female and want to be with men and women. You would probably have to consider the effect of more feminized men as well.
The girl I have been dating has been with 3 girls before I met her. She wouldn't ever call herself bisexual or lesbian, she will simply say she likes pretty girls but would never give up cok. Often when we are out I will catch her looking at hot girls much like a guy does. You would never ever guess that she would be into other girls like she is. She is super conservative and its something you would never suspect.
I'm guessing in her past, not having a guy that would satisfy her sexually opened the door for her to try out females. Her exhusband would basically bust his nut and be done. When she was with another girl, her exhusband sometimes watched, but never participated.
As
@LARaiders85 mentioned, her relationship with her mother did lack some affection.
She asked me my thoughts, and I told her I'd consider it, but only if I was a participant.
One other girl I was with was the same way with women, very sexual, interested in p0rn.