DD is 7. Not 17.
Around beginning of January, her best friend, C (also 7), "dumped" her as she just wanted to hang out with her boyfriend at playtime!
I presumed this would pass but no, apart from a bit of a hoo-ha mid March where another classmate was accused of being in love with C's boyfriend and C got upset and played with my DD for a few days, the relationship between C and boyfriend, A, has stood the test of time!
Anyway, DD found new friends and hasn't been an issue at all. She hasn't seen C out of school at all. Last week there was an evening school bbq and I saw firsthand, that C and A were inseparable, holding hands the whole time and not playing with any other kids.
DD is going to a party on Saturday. DD just told me that C isn't going because "she is going to A's to make love" 
A's parents work on Saturdays and he will be at home with his 14 year old brother. (The big brother was in primary with my DS and has been smoking for a couple of years and spends all his time chatting up girls according to my DS!)
So, here's the AIBU bit. I think, this is none of my business at all and that the expression "making love" is, no doubt just a phrase and these 7 year olds are not going to be having sex
but DH is a bit horrified and thinks I should speak to C's mum. I wouldn't be happy at all for my DD to have this sort of relationship at any age to be honest, (ie, totally exclusive, cutting of from friends etc) but what on earth would I say to the mum?! She must be aware, surely?
AIBU to ignore the whole thing as it doesn't concern me?