Miss Prissy, are the blisters when you are pg an auto immune reaction? With it being on the outside of the joints like it is and not on the moist inside, it looks like an immune response. It could be a systemic reaction to an allergen. I get that with poison ivy only that shows up where ever I'm warm. This reaction is hitting her actual joints.
Did the ER run blood tests. If not, you need to have tests drawn for juvenile rhuematoid arthritis, lupus and such just to rule them out. I am worried about the stiffness in the joints. If it is RA, you can prevent joint damage with proper medication. So it is important to get this checked out. You should see a regular doctor for this first. They'll be cheaper. I am a physical therapist in private practice and I know it's hard to get a doctor who takes payments, but call around until you find one. We do if a person explains the situation and asks ahead of time. They may even have a cash pay rate. Insurance companies pay less than the charged rate so I only ask that amount of my self pay customers. Good luck, but don't ignore this.
Definitely, go for Medicaid. Sometimes they will back up and cover the expenses incurred while waiting to be accepted. You can ask your local office.