Beansy, my DD was like this, she's 5mo now and it's getting better - also have DS 2.7 and he was like this too, so I also felt like I was getting it all wrong - still do some days!
I tried to stretch her out between feeds by taking her out in the pram for a walk, so she'd have a decent gap, and have realised this week that she now goes roughly 3 hours between feeds, altho still cluster feeds in the afternoon a bit. To break the feeding to sleep, again, I've tried to take her out in the pram for a nap, but this isn't always possible with DS (we've got a Phil & Ted's but DS won't always go in it now), sometimes I even resort to the car, just to make that break and get her to have a decent nap. She's slowly getting there - how old is your other DC? - I found that DS always managed to get out a noisy toy when she was going off, but because she wouldn't settle without the boob, I couldn't take her upstairs to try and settle her in the cot as even if I'd fed her, she's wake, get upset and feed off the other side, so DS would be on his own for too long. I started trying to get her to nap in the pram at first, - DS is watching way too much TV at the moment, but I hope to have sorted the sleep out long before it's too much of a problem! at least it keeps him occupied whilst I'm yet again trying to get her to sleep.
I'm still never sure if she's hungry or sleepy or both at times, despite people saying "X amount of time after she woke put her down, or feed her on waking rather than to sleep" - it's sometimes difficult to make this swap. I try now to make a good start whenever we get up (am assuming you're serving at the all night cafe like us or should that be ), so whenever we wake up (anytime between 5.30 (definitly !) and 7.30, then I don't offer her a feed until 3 hours after her last night feed as have realised if I do she'll just snack and take a small amount, then I don't know when she's really hungry and then the snacking would continue all day. What I've found is if I get the first nap of the day right, the rest of the day is a lot easier, so I've found now, that if I feed her in her gro-bag (I use the 0.5 really light summer one for the daytime) then after her feed, I take her to her cot - usually asleep or at least sleepy and then try and settle her without the boob. - It's helped that DH is around at bedtime, so he gets DS to bed whilst I settle DD, so I've started trying to settle her in the cot awake at bedtime first. I rub her back with her lying on her side to begin with, no eye contact, sometimes quietly shushing. If she's being a monkey (adorably so!) then I leave the room and only go back in when she starts to grumble. Once she's quietened down I then leave my hand on her so that she can still feel it there and wait for her to fall asleep. I'm hoping to gradually shorten the process so that she settles without me eventually, but it's getting better. - so the bedtime has helped the naptimes.
I so wish I could say "Oh yes, DD naps and Xa.m and Xp.m." but hopefully that will come over time.
Don't know if any of this is useful, I've rambled somewhat, but I believe 5-6 months is a good time for it to start to come together, fingers crossed.