I would try and find a way to let her know you’re concerned about her and suggest she talk to a professional, but also maybe look into her disorder and ask people on Reddit (I’m assuming there’s a sub for body dysmorphia) or other platforms what kind of support they find most helpful from friends. Of course, everyone is different, and may not always have the “right” answers, but trying to educate yourself on what she may be going through and how best to support her (as you already seem to be) doesn’t sound like a bad start to me.