What the heck is going on with my ex?

Just to be clear we are both females. But we've been broken up for about three and a half, or four months, and she got a boy friend like a week after we broke up, and while she was with him, she would flirt hardcore with me and I would flirt back I thought things were going great, she told me she missed me and still loves me and she would put my hand on her leg at lunch then about a week ago she told me her feelings for him aren't the same and then dumped him a few days later,(they still hang out all the time