Confused

Ok, about 4 years ago my ex-wife kicked me to the curb after 9 years together to be with someone else. We kept in touch because I didn't want to lose a friend. Since then I have a new relationship with someone else. In the last few weeks my ex has been asking to spend time with me. I am afraid she is trying to get back with me. I won't destroy my current relationship because I'm happy. She don't know about my relationship because she had no reason to know about my love life. I told her after her 3rd relationship after me I didn't want to know about her love life. Because all it did was dig a knife into !y back. She asked me to do her taxes that she is perfectly able to do. Now she wants me to go walk with her. I need to some how tell her I have moved on without loosing my friend.