I'm going to get up to go pee while my dog is asleep on my lap.
Isn't your sleeping dog going to fall from your lap then?
It probably would wake her up and make her unhappy.
Obviously if it's an emergency and you really need to go, you should go to the bathroom. However, you should generally try not to wake up your pet who is sleeping. They need their rest and you waking them up would annoy them.
I don't care about her sleep.
Well it would be the more considerate thing to allow your pet to sleep, however it makes sense for you to really have to use the bathroom. Just remember that a pet that gets good sleep is a happy pet!