Snacking?

Baby is three months and eats every hour all day for an average of two minutes a side. I tried doing one side at a time and she still did only about 4 minutes and then just keeps looking at me and gurgling/smiling like she’s happy but then wants to eat again an hour later. At night I’m lucky to get one four hour stretch. I thought at first if I fed her tons during the day I could get more sleep at night but I’m dying over here. Two year old big sister gets woken up by frequent night feeds from the other room and won’t go back to sleep and I’m just too tired to handle this many night feeds. I read somewhere it might be she’s gotten used to snacking in the day so she wants more feeds at night too? She goes to bed awake for naps and bed time and never cries more than a minute or so before putting herself to sleep by chewing her little hands and when she gets up at night she nurses same amount as the day so I don’t think it’s her using me as a pacifier. Am I just doomed to spend the next six months not sleeping or should I just let her cry if it hasn’t been at least three hours and maybe she’ll get used to it? I couldn’t do it tonight when it had been two hours and she cried for 35 minutes before I just gave up and fed her because it’s not like I was sleeping through that anyways. I’m not okay with cosleeping to make it easier btw, I have severe insomnia issues and putting a baby in bed with me is just going to prevent what little sleep I get now. (Which currently is an hour or so during the four hour stretch and basically zero if it’s two hours or less, it takes me two hours to shut my brain off minimum after a feed.) please help me!