Curious...
A 9 year old girl with a boyfriend is too young. Hopefully, it is nothing more than a glorified friend thing, but I would watch closely having 9 year old youngsters calling each other boyfriend - girlfriend. Maybe the term just "friend" would be more appropriate at this age? I'm not being politically correct because boy how I hate political correctness... but quite simply, they are to young to be having boyfriends and girlfriends at that age. that's just a fact.
I would let the "youngin's" alone on this one. they need, at any age, to be able to learn how to handle rejection as it is a big part of life and reality, and no amount of talk from mom or dad can really do anything to make them get over it. That is something the need to reason out for themselves as they come to the realizations of life.
Life can be cruel and harsh sometimes... but we all need to come to grips with that in our own time and way.
Since there should be no life or death serious concerns here, I say...
Live and let live.