It sounds like the new friend she met might have been someone she wanted to be like, herself. Usually we pick friends because of how they make us feel about ourselves. They’re usually someone we admire, want to be like, they make us laugh which feels good, they’re empathetic, they’re comforting — or any combo of those things. This friend may have been a beacon for who your wife really wanted to be, herself. But it doesn’t sound like the friend in and of herself has done anything wrong or been a bad influence in any way other than having had breast augmentation, which your wife realized she wanted, too. Sometimes guys see a buddy get a great new car, and they want one. Or a buddy has a hot girlfriend, and they want one, too. Or a guy may covet and want to have the same jump shot that his buddy does when they’re playing pick up games, so he practices to get that same shot. It’s pretty normal to surround yourself with people who make you feel good or who you aspire to be like. So, I don’t t think, from what you’re telling me, that the friend is really the problem.
And your comment about her confidence really seems to be less about her feelings and more about your fear that you’re going to lose her because she’s more attractive now in a sexual way than she was before the surgery.
What has YOUR reaction to her surgery been? Have you expressed your disappointment? Or have you told her how great she looks? Are you more turned on by her now? Or less? It sounds like the real problem is between the two of you. How has her surgery affected you?