Well...this is interesting.

She's an adult. The man she's interested in is an adult. Where is the issue?
Because she is the senior of the two? Hmmm.

I fail to see where her 'adult kids' have anything to do with her choice of who she has relations with.

I agree with your friend. It's her life to live.
She isn't violating anyone or anything for having interests in someone because he is half her junior.
If she were the 20 year old, and he in his 40's, it's "naturally" acceptable???
Grrrr. This limited mentality baffles me.

If they're happy....All's good...right? They'll have what they'll have, whether it works out, or not. Sooooo....where's the issue? I fail to see one.
But I'm just an old..er woman successfully invested into a relationship with a youngin half my junior, (who is only 3 years older than my own son), so...Imma biased...

Shangrala