Ever just get the feeling you can’t trust someone

Even though they never did anything to you? I’m having this dilemma with my gf , not because of anything she has done to me ,but mostly because I know too much of her past that she hasn’t told me (don’t really need to know ) but unfortunately I do .She even told me she respects me too much that she rather I don’t know about a lot of the stupid stuff she’s done .Just her telling me this I was like (Jesus why did she have to say that ,just don’t say anything at this point would have been way better).Anyways ..... she has a tendency to spit out half stories and little tid bits of info that frankly I’d rather not know at all