I've found girl friendships the worst thing about upper primary for my two girls, far worse than worry about the academic side.
Both have had friend difficulties, but over time, they are sorting themselves out. One of mine is also fickle, and tends to be too much for people, as well as quite disloyal if a better offer comes along. I've told her this but ultimately it is for her to realise what behaviour works and what doesn't.
The other is a little 'marching to her own beat' which then didn't fit with the fairly conventional group she got left with after some children left, she has now, after a year or so, found one or two new friends, so not hundreds, but ones that get her and her jokes.
I'm not saying don't pursue the ADHD side, it sounds like there could be an issue there, but even so, as others say, she will still have to learn to navigate the friendship thing. Try not to worry though, they seem to be practicing from Year 4-6 and perhaps are not all getting the hang of it straight away.
I had few friends as a child, a couple more in my teens but am very sociable as an adult, it doesn't always stay the same.