They hold it at night because they are sleeping, just like people
I would suggest hiring a pet sitter just for one walk in the middle of the day. Pet sitters usually do more than just let them out to pee, which is why they get paid $10-20 a walk. They spend 20-30 minutes playing with them or walking them to wear them out so they sleep til you get home! Doggie daycare is awesome too but you have to find just the right one because she is so small and young. Keep in mind if you do daycare that you really only need to do it twice a week because they get so worn out they typically sleep on their days off.
