The back story in that version clearly shows that she was never really shy. She was recovering from a bad relationship which caused her to lose some of her confidence, and from Tyler's inexperienced POV, he interpreted this to mean she was shy and conservative.
As the Dev states, the girl in that scene was not his girlfriend Rose. In any case, immediately after making that choice, there is a scene where Mark decides to change the app, so that Rose is only attracted to powerful, dominant men like himself. So it's obvious that Rose is never going to become what the MC wants. It was a pretty cowardly choice anyway, which Mark is clearly contemptuous of, so you could make a case that the MC is actually getting what he deserves.
Rose only becomes these people, because the MC agrees to manipulate her using the app. He only reaps what he sows.
The whole BBC thing was originally invented by white American males in the 19th Century, to humiliate black men. So it's fittingly ironic that it's ended up doing the opposite.
It's pretty much impossible to hynotize someone against their will. Unless they have an existing predisposition to accept what the hypnosis is suggesting, conscious or otherwise, it simply doesn't work. So deep down at least, Rose must already have some desire for these things to happen to her. All hypnosis does is remove any inhibitions, that stop you from doing what you either secretly or fearfully want to do.