If she makes little noises and squirms during the night... just wait.. don't rush in, and this may be just normal sleep noises & rustling around and not exactly her "waking up" per say.
If she does wake, cry, need you... then go to her and feed her/nurse her. At this age, you do not want her to "Cry it out." Nor later either. But that is up to you.
At her age, she's probably also changing developmentally and their sleep patterns change too....
Each baby is different, with different dispositions and sleep patterns/abilities.
Your daughter seems to need to feed a lot, cluster feeding... which is common for breastfed. That's the way it is with breastfeeding... every 3 hours or less. As an infant.. they need and must feed on demand. Do not feed her according to a "schedule." Not with breastfeeding. Breastfeeding is arduous... and takes time, and stamina. I breastfed both my kids until they self-weaned. Not easy, but I"m glad, and glad they are done. LOL
I can understand you have your hands full with 2 young ones. But, you do need to feed on demand... "getting" a baby to sleep through the night, especially at this age... is not always easy. AND sleep patterns fluctuate, all the time, and at each growth spurt or developmental change. In your case, maybe your girl is going through a growth spurt... and if so, she DOES need to feed more, and even if she wakes during the middle of the night. They NEED the extra calories and feedings when they are growing....their intake naturally increases.
Also, even though it seems like you are nursing her round the clock, which is normal... make sure that your milk production is still keeping pace with her needs... if not, she may need more and is simply hungry all the time. If she is waking so much, that may be why...she is not getting enough...even though she is at your breast. BUT, if you give her breastmilk in a bottle...in lieu of a direct nursing from breast....this "can" affect your own milk production, thereby decreasing it. SO, keep that in mind.
Direct nursing from the breast, is the best way to insure your body is keeping up with the intake needs of a baby....the body will naturally adapt to the drinking amount the baby is "demanding." Breastmilk output is all about supply and demand and frequency.
When she is nursing, make sure she is nursing/suckling properly. Make sure she is not just hanging onto the tip of your nipple...make sure the ENTIRE areola is in her mouth and her mouth is encircling it.. and you "hear" sucking sounds AND swallowing. If she is not nursing properly...then they are probably not getting in enough intake.
If your girl is waking every hour... first check diaper, check for gas, check for poop. But, if she is hungry... which is probably the case... you want to make sure she is nursing LONG enough during EACH nursing so that she gets to the "hind" milk...this takes at least 15 minutes.. and the baby should nurse longer, to make sure they get the full components of the breastmilk. If she is waking every hour... it may well be a growth spurt and you do just have to go with it and feed her... that is a baby's needs. They get hungry. I too nursed my kids with both breasts at each session... and for however long it took them, and they nursed me dry each session at each breast. My kids also fed a lot. But so it was.
Now, for "Plan B." WHERE is Hubby in all this? He works form home, right? Well, perhaps, HE can be the one to give your girl her "feeding" at night? Thereby, allowing you some needed and deserved rest and sleep. Afterall, you have 2 young babes... and I'm sure he can certainly help run interference for you and pinch hit the feedings at night? Once a woman has 2 children.... it certainly becomes even more imperative that Hubby helps out with things, as much as is possible. Tell him that if a Mama is stressed and does not get adequate rest...it can affect her breastmilk supply. This is true.
IF you do go with giving pumped breastmilk bottles at night... just be extra sure to KEEP to nursing her on demand during the rest of the day and evening... your body should adapt to that... and still produce adequate milk. That is the general logic at least, with breastfeeding and milk supply.
All the best,
Susan