I once had a "friend" who I used to socialise with, was there for her when she attempted suicide, when her DP left her etc.
Was there to support her when she got back with the same DP who she'd attempted suicide over, supported her in her decisions, even to leave her job and move cities.
She had a huge leaving do and didn't invite me, but invited someone else who she was supposed not to like, and I found out about the party off him.
When DP left her again, and she attempted suicide again guess who she called. I supported her through this episode again and when she was strong enough I asked her why she hadn't invited me, she couldn't or wouldn't answer me, so I told her she had hurt my feelings, I didn't condsider her a friend and until she could come up with an explanation, apologise and make up for it she never would be.
Haven't heard from her in years.
Some people are just so self absorbed and think that you are there to do their bidding and like to show off the good times to their fair weather friends - and use the true good people when they need to lean on someone.
If your children get something out of the friendship then support them in it, but don't waste your time or effort on someone who just isn't worth it.