try not to compare, as it's impossible to know what exact factors might be the ones impacting their bubs ... is it formula, or more feeds, or genetics, or something else altogether ...

try also not to beat yourself up - you've just had a baby, you're getting used to having two babies, recovering from the birth, and getting used (again!) to feeding, waking at night, millions of nappies, and all the rest of it ...

and then talk with your DH, and decide what is best for you and your daughter.

personally, as I only had a short time of maternity leave I expressed quite a bit and DH did one of DS's feeds from the day he was born - so I always, *always* had the option to get at least one decent few hours of sleep (as even if I got up to express, you can do that almost asleep...). it made a wonderful difference for us. it worked for us. that might not work for you.

if your DD is having a growth spurt and just needing extra milk for a few weeks, staying in a routine and keeping to breastmilk would obviously be the best option for her, for her digestive system and immune system etc. she will go back to sleeping through before you know it.

is expressing something you'd be willing to give a crack? that way your DD can keep having breastmilk, but you can get some reasonable rest, if your DH does either the last night or first morning feed ... ?

there are potential down sides with formula feeding, as I'm sure you'll already know. but it's understandable for it to be tempting when you're tired and sore and wanting to sleep etc. you're not a bad person or a bad mother if you comp feed.

have a good solid think about what you want, what you can do, how you'll feel about the different options, and how long you're prepared to try different things. talk with your DH. talk to the ABA to get some tips from them too. don't make ultimatums or hard and fast rules for yourself, but do have a flexible plan in place.

big hugs whatever you decide

just listen to others' ideas and opinions, then decide what works for your family.