I'll say it:

I think this is normal behavior. People react to the presence of others they are attracted to or others who seem attracted to them. They also react in relation to the partner and those who seem attracted to their partner. This sounds like such a perfect example of the little subconscious ways people exhibit desire.

In fairness, maybe you're paranoid ... but it's just as likely your wife was just being human.

For instance: If you go to a party where there are lots of good looking members of the opposite sex who seem taken by you, your spouse is suddenly far more likely to demonstrate a public display of affection or somehow else exhibit the connection you two have. Alternatively, she may somehow reduce your value relative to other men in the space: Mate guarding (it's not a PUA term ... it's a biology term, and it happens)

Likewise, if she is talking to a man she finds attractive or notices a man she finds attractive, regardless of her devotion to her spouse, she will engage in all the subconcious preening behaviors, body language, etc, and distance herself from you.

You do it too.

Next time you're among several men, take note of the "posturing" they do. It's fascinating. I suppose you never turn your head at a sundress, sandles and long wavy hair?

It's perfectly normal human behavior. Usually we can reason ourselves away from caring and often we can engage our faculties not to behave like we have constant underlying sexualities ...

The fact is though, we're animals. No matter how much your wife wants you and loves you and your kids and your marriage, she'll still get a little flustered by a handsome stranger. It doesn't mean she wants to drop you ... just that her body wants to increase her odds of reproducing with a desirable mate.

I don't think what she did was disrespectful at all though. It was well within the realm of normal human interaction in that setting. She was defensive because she was probably not even aware of her change in behavior.