She still might be too young to hold it throughout the night! Try taking her out to pee (on a pad or whatever) around 2am. I don't know when you go to bed/wake up, but 8 hours or so is a long time for a little baby to hold it in! Most pups don't have full control of their bladder until they're about 1 year old.
When you take her out - don't talk to her (aside from "go potty" or whatever phrase you say) and don't play with her. You want her to know that this time is strictly for "business" and nothing else.
You'll have to do it for awhile, but I'm sure you didn't get much sleep when you had your baby son, did you?
Good luck!