I have a snoozer scalloped dog ramp for my bed, so my dog can get on and off as she pleases. IMO it's the best option out there for very small dogs, she was maybe 3lbs when I got them (7lbs now) and used them without a problem.
I have a pee pad in my room for her, she used it regularly as a baby but now she usually waits until we go downstairs. She also used to need a nightlight to find the pee pad.
If you do this, just make sure there's nothing she can get into while you're asleep.
Snoozer Scalloped Dog Ramp | Stairs | 4 Colors + 3 Sizes