It sounds like she continues to have issues with the ending of your relationship. If she really wanted to have it be over, she would stop all contact. It may be that your efforts with going to the gym and your weight loss has gotten her attention. But that would not be a fair reason to keep in contact with you. That would be based on image and not who you are.
It depends very much on how you feel about this continuing contact. If you feel you are ok with it, then keep going and see what happens. But if you feel there is no resolution and she doesn't get how you feel about her, then you may want to unfriend her and let this contact die out.