Girlfriend peed after as I fingered her...

I can usually make her squirt rather easily, which is very sexy albeit very messy too. We're both fine with that, it's cool.

But this time I fingered her particularly hard (like she asked, well screamed for) only as she cummed she kinda peed. A fair bit. It was a lot more than a usual squirt and it stunk of pee, so we're fairly certain it was a wee. We both thought this was not possible? To pee as you orgasm?

Please, somebody enlighten me. She's afraid to let me finger her incase she does it again. There was quite an amount aswell.