Ladies please......girlfriend insecure from weight gain?

I've been seeing an older woman I met on Yahoo personals for about 6 months. She's in her 40s, divorced has 2 kids in college, but she has a great body and shes amazing in bed. I go to her house every morning before work for . She has put on about 15-20 pounds this winter and now she's insecure when we're in bed. Personally I love the extra weight. Her body is thick and soft, she now has a bit of a roll around her stomach but her have gone up almost two cup sizes. Although I can't keep my hands off her now and I keep telling her that the extra weight makes me hornier, she doesn't listen. Today she didn't want to get on top during , she didn't want me to look at her fat stomach and drooping s(her words) and she didn't want doggy because now she feels its degrading. I love her new body and cant get enough of it but her low self esteem is depressing as hell. Any suggestions on how to change this?