Cheating wife or lucky husband?

My wife is 44 years old. Our son is in college so we are empty nesters. She was a modest, even boring, dresser for most of her life, either at home, at work or going out. I suggested a few times she could go just a little racier, particularly when going out, but she used to brush me off. Then a couple years ago or so she started trying on new things -not because of me asking, since I had given up a long time ago, she just got started on her own. Make up for work (she used to even attend parties fresh-faced), slightly shorter skirts, jewelry, heels (which she always hated since she is really tall). For a while I was just pleased with the change, I complimented her looks, and she seemed delighted.

And then at some point it began going a little too far, ort at least I felt that way. Makeup became heavy, jewelry became flashy, skirts became mini, heels became really high. I commented on her choice of outfits -calmly, not making a scene or sounding judgmental- and she happily answered that she just feels great, thinks she was too shy for too long and now she wants to enjoy her body while she can (she is in great shape for her age). I have no real reason to assume she is having an affair, she is back home at the usual times, no unexpected urges to go out somewhere on weekends, and her behavior towards me has not changed, she is sweet but neither too much attentive nor snappy or angry. I know her cell phone's password and she makes no effort to hide it, and there have been no surprises with our shared bank accounts. Last time we had friends for dinner I could not help noticing my friend -an old buddy of mine- staring at her, and being embarrassed knowing that I saw him. His own wife -a sweet happy soul who often seems clueless- chirped how great my wife looked, even made her parade a little for us guys, which was downright torture for me. After they were gone I cautiously discussed the night with her, she laughed, called me a silly jealous guy, and pointed out that my friend is not quite the prize (which is true). She says she just dressed like she always does -which is also true these days- and then admitted she notices and likes the attention. But she swore there's nothing else going on.

I have to mention I'm older than her (54) and I pretty much settled down for a bit of a beer belly and t-shirt look, so I admit I feel insecure about the rather obvious contrast with her. She has never said a thing about how I dress or how I look, and for a long time she dressed the same way although she has always been slim.

So where do I stand now? Should I be happy knowing I have an attractive wife who loves to dress up and perhaps be a bit of a flirt, or am I a naive old guy who is losing his wife to somebody else (I can't even begin to imagine who) and is doing nothing to prevent it? Has anybody here (husband or wife)gone through a similar experience?