My new girlfriend "doesn't understand" relationships.?

This is a situation I've never been in before, I'll try and keep it brief. I got together with a girl I used to know years ago as kids..talked on FB for ages before we actually met up, and she said she loved the fact I wasn't like "other blokes". we used to talk for hours on the phone and got on great, but like any decent mum, she ws worried about introducing someone new to the children.After a while we met up, and really clicked and the kids old her how much they liked me etc etc, so I thought everything was going great. Had dinner with her mum, brother etc one day and they said it was great to have someone around that treated her and the kids so well..... then out of the blue she "vanished". no replies to texts, no answer when I called etc, and deleted on FB. I tried for ages but got no response, so tried to forget it and move on. that was 3 months ago. it was her birthday recently so I sent a one off text wishing her a happy birthday, and she replied! I ws over the moon! we have been talking again recently, although its very patchy, but when I try and ask her anything to do with "us", she clams up, and says she "doesn't understand relationships, whats the point". She says she likes me, she says I'm a really nice bloke, and its great the kids like me. but its almost impossible to get her to talk about anything to do with having a relationship. she has strongly denied having anyone else, and I believe her. I'm being patient, and most people would just walk away, but I can't, I really think we could have a great future. Does anyone have any ideas how to deal with this, If I come on too heavy, I'll scare her off again, and probably lose contact, but its driving me crazy not getting any straight answers. PLEASE HELP!!