I’m sorry OP. And sorry for your daughter to have to go through this. There is nothing you can do other than support your dd through this tough time. and realize she is only 13 - not really old enough for “serious” relationships, regardless of being gay or straight. This could have just as easily happened with a boy.
It’s great that your dd is comfortable with her sexuality and that you are comfortable with it also. But you both need to keep in mind that many people won’t be okay with it and you can’t *do* anything about that.

Just offer your daughter sympathy. Treat her like any kid suffering through a break-up. You can't go against the other person's wishes.

DD (13) has a girlfriend - they have been dating since December and are best friends. The other parents are not ok with their daughter being gay. Now that school has ended they are banning their daughter from seeing mine. They have also limited phone access between the two girls. As you might imagine my daughter is devastated. I’m not sure what I can do - if anything - to help. Any suggestions?