My daughter has had fever for 5 days and now a rash, what can I do?

My daughter has had a fever for about 5 days. Today she developed a rash that looks to me like hives. When her temperature rises she often will complain about headaches, stomachaches and muscles aches (feels like she can’t hold her head, legs hurts, etc). She has seen a doctor 5 days ago when she was on her first day of fever (her sister was on her 4th) and the outcome was that it was viral, no infection. Her sister has stopped her fever after 4 days and is in awesome shape. They also both tester negative to COVID several times, including today.