J.C.
I would request a meeting with the teacher and behavior person that she has been seeing. Then I'd ask for their input on what do to next. Lots of kids need help knowing what to do to make friends. Then talk to your daughter about the things she's doing that aren't friendly and why.
I'd also ask your daughter who she thinks would be a good friend for her and give her some ideas of how to make friends with that child - draw her a picture at home and give it to her, write her a note, ask her to play at recess, invite her for a playdate, give her a sticker or gummy worm, smile at her, etc. 1st graders are very forgiving so even if your daughter did say or do some things she shouldn't have, it doesn't mean the kids will never like her.
I'd also give her some ideas on what to do if someone isn't responding the way she wants - like if she wants to play with a certain person at recess and the person isn't being nice, walk away and make a new friend.
I teach kindergarten and this is VERY common. I know it is probably heartbreaking for you to have your daughter struggling...don't worry, it will pass and she will have learned a lot! Make sure to connect with the teacher about it...he or she really can help to encourage friendships especially in first grade. Good luck!