My Niece Is 22 Months Old And Has A Rash

My niece is 22 months old and has a rash on her front and back side covering from her neck to her waist. She has an elevated temperature, runny nose and a bark sounding cough which has increased throughout the evening. Her groin area was a bit red with no rash noticed. She developed this rash around 6pm tonight when we noticed it. It does look like she is teething at the back molars. The runny nose has also been associated with her teething in the past. She had Advil @ 6pm & Tylenol at 9pm. We are concerned for her and especially since it is Easter dinner tomorrow with quests coming over.