Twins! How fun! I bet they are darling!
What you are describing sounds like a canker sore or actually a sore that's been caused by your daughter's little lip not used to having teeth there. Her little teeth could have worn a sore there. Please don't worry about it too much until you hear back from the doctor, especially if she doesn't have a fever and she doesn't have those types of sores anywhere else in her mouth. And you would most likely know if it's really hurting her. It might be best to leave it alone....it will probably just go away by itself.