Don't be hard on yourself. You are insecure about W looking good and getting hit on by some hunk of a man that sweeps her off her feet -- no? I can relate because I've been there too (still kind of there, but working on it). Having the security and self-confidence to say, "Damn honey! You look slammin' hot in the dress!" (or something along those lines ) and then with an upbeat tone say "Have a great time with the girls," you are exhibiting a behavior that would be attractive and appreciative to your W. She likely just wants to go out and be noticed -- that's all.
I once heard Michael Irvin (you know, the ex Cowboy wide receiver) say that "When you look good you feel good." That's all it is about regarding your W IMO. Every Monday night I go out dancing from 8 to midnight. I make sure I'm dressed to impress, that I smell damn good, and have an air of confidence about me. I dance with so many different women it's insane. I socialize with them and thoroughly enjoy myself (all of this formerly out of my comfort zone). Have I been hit on -- sure. Have they been good looking women -- absolutely. Could I date any of them -- definitely. Do I initiate anything that would lead to that -- no way. That is not my goal. That's not what I'm there to do. I'm there to enjoy the hell out of myself, dance my arse off, and feel great about myself as I do it. My point here is that it's great to get noticed (great for the PMA), but that doesn't mean I'm looking for anything more than that. I'm sure your W feels the same way.
Don't know if this makes you feel any better, but my suggestion would be to tell her how great she looks, to have a great evening, and never say another word about. Don't ask about it (aside from "did you have fun with the girls?"), don't seem jealous or worried about, and don't dwell on it. You can't control it, and trying to would do more pushing to what you are worried about than sitting back and playing Mr. Confident.
) and then with an upbeat tone say "Have a great time with the girls," you are exhibiting a behavior that would be attractive and appreciative to your W. She likely just wants to go out and be noticed -- that's all. 