What Is The Severe Pain Along With Flu Like Symptoms And Heavy Bright Red Discharge?

Hello, my daughter is 11 years old and this is her third period. The first ones were normal beginning periods (light and brownish in tint). Yesterday her period came again and today she is in tons of pain, flu like symptoms but no fever, and a heavy flow of bright red blood. The issue is that she has had a clear fluid along with her period. She thinks it is blood and goes to the bathroom to find out it is not. She isn t on any meds... Is this normal or should i take her in?