My DH and I have come to the conclusion that I need to figure out pumping (now that someone got me the Medela hand pump) so that we can have a night to ourselves.
I read while researching online not to put more in a bottle than your baby takes at each feeding. I have no idea, though, how much she takes at each feeding! Is there a way to find that out short of purchasing a baby scale?
Re: Pumping help? Trying to figure this out...
Start small. Like, half an ounce. If she's not used to taking a bottle, she may fight the first few bottles and only take in a few fractions of an ounce before "figuring out" a bottle. DD really fought taking BM by a bottle and we lost quite a few ounces at the beginning. Have a few plans for how to get her to take a bottle. Nurse first, then introduce a bottle for the last little bit seems to be the easiest way, since they are pretty relaxed after nursing and less likely to fight a new thing.
Once she has the hang of it, I would do what PP suggested and start with 2 oz bottles and have ~1 oz bottles as back up. I think as long as you get close to about what she would take by breast, you're okay. If she's not totally full, she'll likely just be hungry again sooner.
I'd just start with small bottles and try maybe once a day. Go slow and see if LO seems hungry after finishing. If so, just nurse and try a slightly bigger bottle the next day.
You'll need to get LO used to the bottle at home before leaving LO home with bottles, anyway since that could be super stressful for the person watching her. At one month I would assume 2-3 ounces, FWIW.