I can't speak to the context but assuming this is not a reverse lesbian cure with porn latitude, there is the possibility of situational sexuality, most evident in:

• Prisons
• Traditional (men only) navies
• Gender-isolated schooling
• Cloistered communities where celebacy is mandated.

So the non-rapey possibility is that they're isolated from men for long enough for attitudes to change.

Here in western (Christianity-informed) society our squeamishness about sexuality only exacerbates the effects of situational sexuality. The Navy will literally awaken your gay. (assuming you have a normal libido.)