Yeah, I did realize some of those clues about her past but it was still kind of unclear to me. Don't get me wrong, having those clues scattered around and influencing her actions did make it interesting to theorize about what could be that secret. To be honest, what bothered me in particular was the fact of her telling Jack about it and then the game simply "hiding" it from you... maybe the real issue was just my own curiosity.
I also felt like it could be more interesting if the story developed more about that "secret" as it would make you sympathize even more with Grace, but that's just an idea of mine. She's a great character overall.