it would seem to me that the pressures of every day life got too much for her and as always when we crack under pressure we take it out on the closest people to us.
i suggest meeting again-you have nothing to lose,listen to what she has to say maybe she can explain in depth why she felt she had to leave u,but i think she has realised it wasnt u that is her problem but something else...
i would advise explaing how hurt u were from her leaving u and that u cudnt do that again,she must be insecure and unsure of herself so be the strong one

good luck