DD1 hates DD2s friends

[sandbagsatdawn]

Wondering if this is a common problem or just a thing that happens in our family. DD1(10) and DD2(8) get on pretty well. They have their moments obviously when they bicker but hardly ever have major fights or fallings out.

However, DD1 always seems to have a problem with DD2s friends. She is hostile towards them when they come round, and they are hostile towards her (I'm not really sure which started first). They seem to go out of their way to wind her up, and there have been several occasions when DD1s stuff has been damaged by DD2s friends, or they have had a big blow-out, eg a friend of DD2 ended up throwing DD1s drink out of the window. This happens with all three of DD1s closest friends, who are all quite different from each other (and one of whom doesn't know the other two).

I've never had issues with DD1s friends and DD2. They either ignore her, or behave perfectly normally and friendly towards her. DD2s friends are also fine with DS (6), though ocassionally tell him to leave them alone, they don't seem to pick on him in the same way as they do DD1.

I've tried telling DD1 to stop being so negative and antagonistic and then they will do the same, but in some ways I have sympathies with her as they do seem to go out of their way to annoy her. She also has a tendency to hold a grudge which doesn't help matters, as once someone has crossed her she won't let it go.

I've tried having DD2s friends round when DD1 is out, but that has been the cause of problems with DD1's stuff being "accidentally" damaged or "mysteriously" disappearing. (In fact on one occasion one of her books was drawn on which was definitely not by accident.)

I've also tried each of them having a friend at the same time but the two pairs then seem to rub each other up the wrong way and niggle at each other with little comments etc.

Any suggestions?? Is this just going to get worse as they get older? Dreading the teenage years if so.