You really do need to sit down and have a conversation with her no matter how difficult you find doing that. She cannot make you feel guilty for having sex with her that is just wrong on her behalf. She obviously has some serious issues and you need to sort that out now. If she makes you feel guilty for having sex then that will just grate on you over time and you will become beaten down by her. You have kids to think about so talk to her as soon as possible and get it all out on the open. You are both young and she is probably going through a confused stage she may need some reassurance from you.