At this point, I think it is half her guilt and half her longing that make MC still think of her old lover. Different people grieve differently, so I do understand her still not being able to let go. However, I see it as a good sign that she has been thinking about him. She has been ignoring the issue so long by claiming not to be interested in love and marriage, but now she is forced to think about it. She is finally facing the issue. She is changing (hopefully). The process might be unpleasant, but I hope she learn to finally let it go and be happy.
And Sid, while I do like you, you shouldn’t put the lady on the spot like that. I do understand your shock of suddenly being told that the lady you’re interested in has someone she loves (who is not you) though.