Board Thread:Spoilers!/@comment-4936165-20140827005907/@comment-24674051-20140918155754

She told Regina that she had moved on, but that was before the curse. Hard to say what being trapped for 28+ years will do to a person's psyche. She may have come out, and decided (particularly after getting her head handed to her by Emma, of all people), that it is time to take off the gloves and come out of retirement.

Of course, having that bottle of love in an egg shoved inside of her for at least 29+ years (28 for the curse and at least 1 for Wedding/Pregnancy) may have somewhat affected her while she carried it, but now that it is out, she is free to carry on with her evil and malicious ways. (I am assuming that David's encounter with Mal was before the conversation between Regina and Mal in 1.2)