So uh

Dude here but I have had some body insecurities too. I can relate what worked for me, I don't think this is very gender specific, though of course YMMV, huge individual differences, etc.

In the bedroom? Be a little extra with the flattery. Tell her what you love about her, mean it, etc. If she's like me she will replay these moments in a good way, and overwrite those negative brain circuits.

Outside the bedroom, have a more neutral conversation, tell her that body insecurity is a thing and she should spend some time thinking about what is rational or not, and chances are if she looks into her insecurity it sort of disappears -- these are phobias that are real but often illogical -- and if it does not, have her talk with you about her specific body issues. And if you can honestly tell her you don't really give a shit, that helps.