I would first off ask to see her in person, and get your ownership in writing. That way, you legally own him, and there's no questioning it. Through e-mail it can still be questioned.
I would also tell her no, not right now anyways.
I'm in the same situation with my horses old owner. She contacted me on FB and keeps requesting things, and I don't want my horse around her again. I just ignore it. It's rude, but I can't risk him.