Imo it is a good idea to have a plan before you go in to see the school as to what you want them to do and what they can do.
Telling the little girl she must drop her new friend and play with your dd is clearly both unfair and unrealistic- and you would not have been very happy if the school had done this to your dd when she first made her friend. Even telling someone who they must be friends with - well, we wouldn't accept it as adults and there is no reason a child should either.
Asking them to keep an eye out for any unkindness or bullying otoh is a reasonable request; if this new girl is being actively unkind she needs to be stopped.
Otoh asking if there is a mentoring system/place to go for children who have noone to play with is a perfectly reasonable thing to do and the school might want to think of such a scheme if they haven't already got one.
And just letting the teacher know that your dd is feeling a bit fragile atm.
Also chatting to your dd as a parent and explaining that these things happen, that friends change and you make new friends and it's tough for a bit and then you feel better.
Perhaps giving her some hints on how you can make new friends. Do you think she is very shy? Bossy? Only willing to play on her terms? Or do you think it might be a temporary problem and that she will make new friends if she is just encouraged to hang in and not lose heart? Could you encourage external interests to help her make new friends outside school? Sports? Drama?
As for the recognition, it is going to be virtually impossible to prove, you have only your dd's perception to go on and it's a fair bet that she doesn't notice when other children's achievements or good behaviour go unrewarded.
I think here you can do a lot as a parent by explaining what it's like to be teacher and have so many children to look after, that it is easy to miss things, but it doesn't really matter because her good behaviour and learning will serve her well in the long run.
I used to get this a lot from dd, probably at a rather younger age than yours, but it was very similar: I never get to be Star of the Week, I never get a good part in the school play though I'm the only one who can learn lines etc etc.
She may well have been right about every individual complaint for all I know (how can I know?) but I felt encouraging her to nurse grievances would not be the best way to help her. I found the actual complaint hardly ever mattered in the long run (who cares six months later if they got to be Mary or a reindeer?) but the right way of listening did matter. I worked on hard on cultivating the right vibes: "yes, dear, I can see you are upset, I can't know what's wrong or right, but I do sympathise and I am sure you'll feel better soon".