You have to get her lingerie that isn't too tight. Think babydolls and when she is wearing it tell her how sexy and beautiful she looks. It is probably the best idea to shop with her and you two pick things out together. Make sure you get the right size. Too small and she feels to big and if you get a size too large it might make her feel bad as well.

My wife doesn’t like her body and I tell her all the time I have the hots for her. I wish she would wear lingerie more on her own and surprise me. I usually have to ask her to wear something nice for me. I also usually pick out and buy things on my own. It’s hard to buy for the right size especially when ordering online. I’d like to go together to pick out things that we both would like one day. I just keep at it and tell her she looks great. You could try sleep wear that’s in between that and the look of lingerie. I got my wife this nightgown type piece that is really soft and is solid but has small lace cutouts below the breasts. It’s pretty casual but shows off her breasts a little.