My girlfriend peed the bed?

I was lying in bed last night, my girlfriend was asleep and then i felt this trickle of liquid. I turned around, lifted up the blanket and noticed that my girlfriend was peeing. She hadn't drunk any alcohol so i'm a bit confused as to why it happened. I woke up her and gently told her what had happened, she got really embarrassed and started crying. After she'd showered and changed, i comforted her and let her know that it was ok. But i have a couple of questions about it.

1) Should I have woken her up?
2) What could have caused this? Could it be physical, psychological?

She witnessed a lot of abuse during her childhood so could it have something to do with that? Please help

(She's 22 by the way if this helps)
My girlfriend peed the bed?
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