This would bother almost every guy so it's definitely normal. From what you mentioned about being in long term relationships before and her situation, i'm not so sure this will work out but i guess time will tell. It depends on what you can and cannot accept in her past and possibly what might happen in the future. I think it's wrong for a person not to tell something such as this simply because if it comes up later on, it might make things a lot more complicated (it usually does). This way, you can either accept it and move on, hopefully making things better in the long run, or just ending it.
-to be nobody but yourself in a world which is doing its best, night and day, to make you everybody else means to fight the hardest battle which any human being can fight; and never stop fighting.- e.e.cummings