Should I worry about my wife's attire?

If you want my opinion, if you really trust your wife, you wouldn't be worried about this. It's her habit to do this, so let her. All I wear to bed is panties, and I'll do that if I'm home no matter who's there, because it's comfortable. I hope that makes you feel better. Oh, and the friend- if he's known her for 10 years, he's probably already aware of this habit.