You might want to settle down and figure out if you really are OK with this. Sometimes people only feel they have unmet needs because their spouse does. And that is a very normal reaction to have.
Sometimes it is less about the sex and the feeling of falling in love, and more about craving some time without having to be responsible.
Being a parent is an awful lot of responsibility that if you two don't find healthy ways to relieve that pressure and get a "vacation" from those responsibilities you will find yourselves filled with resentment and bitter
and it is something all parents have to deal with, I guess you need to take a moment to honestly figure out whether or not you will be able to handle this. It would really help of your wife chimed in too, as it almost sounds as if both of you are having trouble being getting relief from the pressure of life
Was she honestly upset that the flirting was returned?
that is being respectful until they understand that you are OK with that.
It sounds like your wife is in such a need to get a break from being responsible, that she is about to pop
might want to take some deep breathes, you really need to figure out what is really going on and how you are going to deal with it