My friend threw water on me to wake me up.
Are you a deep sleeper or something?
She thinks I usually sleep too much, sometimes for days.
If you sleep for days, maybe throwing water on you is a good idea. It's really bad for your health to sleep that much.
I shouldn't have to get out of bed until I want to.
Normally I'd agree.  However, there are serious health consequences to oversleeping as much as you're indicating you do.  I think your friend was just looking out for you!