Your rabbit likely has a severe bacterial infection/abcess in her mouth and
gums. This may be related to the
teeth not being trimmed regularly, or to a sharp piece of hay or wood that penetrated her gums. This is a very serious problem, and you should see a veterinarian ASAP, because if she is untreated the infection can spread and cause her death. She will likely need antibiotics and possibly surgery to remove the infected area.