After sex, girl felt pain in vagina.as if something was repeatedly hit. within hours panty had clear discharge. like she peed.on herself. normal?

Vaginal discharge: Clear post-coital vaginal most likely a mixture of normal vaginal fluids as well as semen. Of course, would've been better for guy to wear condom to minimize risk of pregnancy & sexually transmitted disease. This would also minimize clear discharge later on.

No not normal: The pain with intercourse should be evaluated by her gyn before you have intercourse again. The clear discharge is probably just semen making its way out if you had unprotected intercourse.