> because it is relatively easy to be a frum girl.
I came to a similar conclusion – it is easier to want to marry T’Ch than to actually become one. Even your list of a “frum” boy missed a “couple” of things – derech eretz and derech eretz (middos and earning an honest living).
Is it really easier to be a yeras shamaim young lady than bocher? Probably not, if her education would focus on middos, professional education on how to be a teacher (future family or school), earning an honest living, etc
At the end, the explanation is probably biological – males of all species and nations are prone to more risk and deviation from the norm.