Ok, so to answer questions...
I'm not going to immediately dump a very close and old friend because of an issue that can be resolved. Is this really how people treat their friends?
I do tell her DD off, I am firm with my "Do not hit me", palm up in front of her and stop her hand if I catch her doing it.
I haven't mentioned it to my friend yet because, aside from being utterly crap at confrontation, our different parenting styles are a bit of a bone of contention. Not sure if anyone will remember a thread I put up in the summer...TL;DR version - went on holiday with my friend and our 2 kids each (both have kids who are 4 and 8). Her 8yo's awful behaviour - over reacting, constant screaming and tantrums - was ruining it for my DD and we ended up leaving. We left on very good terms though, my friend understood and accepted her DD was challenging.
Anyway, since then I raised the issue that her 8yo may not be NT like she thinks - and she shut me down. Has no concerns that her DD is anything but just very sensitive. So since then really I'm reluctant to point out, yet again, that I think there are issues around her children. Should maybe have mentioned that in the OP but how early didn't want the OP to be a novel, and it may not be even relevant.
So anything I say may hit a nerve...I dunno. I might wait and see if it happens again and then say you might have to tell her off as she'll only do that at school.
Also, I'd love to meet my friend on an evening but I'm a single mum so can't leave the kids alone, and she would be more than welcome to come over but her DH refuses to watch the kids, even when they're asleep. Yes, he's a massive prick.
Or have some fun. Show the girl a lolly and tell her that it was for her but now she’s hit you she can’t have it. Then happily eat the lolly yourself without hesitation
That's vile behaviour, I would never do that.