Difficulty with advisor's specialty
You seem to have answered it yourself, and I'm pretty sure I agree, though it is just opinion. But I'd suggest that you evaluate your options in terms of what will get you out the door fast and successfully rather than "liking" what you are doing right now. You will have the freedom to follow other paths if and when you successfully finish. 

You like your advisor, she seems to be good for you. Too many students don't have those advantages. Working without an advisors advice works for some, but not everyone. 

It might be worth having a chat with her, expressing your difficulties and asking for advice on how to quickly gain insight into what she does. Not everyone knows how to provide that, but if she does, it could help situate you quickly.