Wife has negative feelings about her body

We had our 2nd child 4 months ago. My wife is super sad about having a “belly” or squishy tummy that hasn’t gone away. I tell her a lot that she is beautiful and that I find her very attractive but it doesn’t make her feel better. I honestly love her and her body. No matter what I say she is still down about it. I think it’s something she needs to come at peace with. What can I do to help her? Is this a time where is just have to shut up and listen?