Reading through this thread has given me plenty of time to think. I doubt I could have come up with either of these responses in the moment.
On the flashing, I'd say in a superficially sincere way, "Oh, a hot flash? Go ahead and take your shirt off, I don't mind." Hey - that's not rude, is it?
I am a lot older than my DH, and obese - and he loves it. she'd probably write me off as "no competition." So this next plot would probably just fry her buns.
I'd walk up to her - ignoring him for the moment - and say, in a shocked and confused voice, "What are you doing on that man's lap? Can't you see you're embarrassing him?" After she moved, I'd say, "Hi, sweetie," collect a little smooch (our usual greeting) , and sit down.
Of course, that's assuming he hadn't already taken care of the problem. And he's quick on the uptake, too, and might, um, exaggerate that smooch for her benefit...
No, I'm not going to blame a man for not reacting. Think about it folks; how many of us react to insane rudeness with shocked silence? Why should being male make a difference?