I have told my partner (in the past) that i have been hit on. Mainly because it fits into the "how was your day" question....and it more or less lets him know that "hey this person found me attractive, yet im here with you telling you so"
I spose it is all about the relationship and how secure either party. Unfortunately my ex was a jealaus overbearing ****...so his reactions usually were i wasnt allowd to go near that person.....
My favorite thing he would do is he thought i was going to sleep with the people i worked with and wasnt allowed to go have a drink with thim.....They were all women. I didnt go though the pain and suffering of comming out ot my family, parents, and coworkers only to turn back....Sheesh
So in conclusion, yes I tell them if i have been hit on......But if it is a close friend of both of yours then the situation gets a bit more tricky, and may have to dealt with privately (hopefullly privately means telling thim no and never to do it again, and not a quick snog in the bathroom
)