This is a tricky one. As long as you keep your posts neutral and maybe discuss this request with your son. He shouldn’t mind, but if it does freak him out, don’t accept the request. Either way, you are best talking to your son about it. Hopefully he’ll be fine with it, but it is best to be sure. And if you become friends on Facebook with her, just avoid serious/relationship topics. [But you aren’t stupid and know how to be tactful.] Just keep it light hearted as you would with other friends on Facebook.