Talk to the guidance counselor.
The school may have a program in place or something to do to help. For example, our middle school had a "nobody eats alone" goal so that by the end of second week of school, everybody had a group to sit with. They challenged the kids to be inclusive.
Then as the year went on and some kids were annoying or were ostracized for other reasons, they asked nice kids to take them at their table. My dd's table was one of these tables where they knew everyone would be accepted. Some kids had been bullied.
So, ask them to do what they can to put your dd with nice kids. By now, they know the groups that are fluid and easy to break into vs the groups that are more rigid and maybe more visible.
I agree ask the guidance counselor. Hopefully there are kids they could try and connect her up with. I bet your daughter isn't alone and she really only needs to find one friend to make thing better. In junior high girls become really catty, social groups are constantly being rearranged and it doesn't take much to be on the outs.
As to the "no one eats alone". My DS's junior high tried this when DS was in 8th. DS ate alone out of CHOICE in 7th & part of 8th. He found empty table and read quietly during lunch. At the time I think he really needed the space from being forced to be social. He HATED it in 8th grade when they instituted a new policy that forced him to share space with other kids. Although after a few months of gripping it actually did work and he did finally find some kids he didn't mind sharing a table. DS is 16 and a junior in H.S. and honestly it did get a LOT better.
But your daughter isn't my son and clearly doesn't want to be alone so I would defiantly try and get school to intervene. My district offers social skills groups run by a social worker and I recommend you ask if they have anything. Directly working on social skills with a small group can be really beneficial to any kid struggling socially.
