This really isn't healthy. You don't need her approval for anything. I think you really should quit all contact with her and move on from it. how long do you want this to go on? Do you really want to say "I'm obsessed with my husbands ex" forever? I sure hope not.....
I think about my DH's ex-wife sometimes because she and her mother did all they could to make our lives hell. I'm not jealous of her, actually she's jealous of me because she wants him back but he hates her. When I think of her, I picture karma biting her in the butt. I also hope I'm there to see it after everything she's done to us.
I've never thought about my husband's ex's at all. Now on the other hand my husband was very jealous of the guy that I was "friends with benefits" with before my DH and I started dating again. However, my friend sat down with my husband and they talked. He told my husband about how I talked constantly about my DH. (My DH and I first dated when we were 15. Then again when I was 22 and again when I was 28.) After they sat down and talked my DH realized that the past is the past. We are here in the present and he's the only man that I love. They hang out together now. I'd say you just have to remember you are your husband's love now and have been for atleast the past 12 yrs. Ex's are ex's for a reason. :)