My first daughter was tricky with milk at that age. She never had anywhere near 18oz in one day after 6 months. I would be careful with the squash though, it fills them up and is limited value. All this they 'need' 18oz or whatever makes me laugh because they won't all take it regardless of before meals or whenever. My other one happily guzzled it back.
The way I look at it is I'm 35 and we were all put onto cows milk at 6 months.
FWIW she' s now 3.5 and actually quite likes milk
Just keep offering but also put formula milk in meals and on cereal.
Stop with the squash and the milkshake powder! Both are loaded with sugar and have nothing of benefit to your baby in them. Presumably she's still having several bottles a day at 4m - milk should still be her main source of nutrition as her body can't digest solids properly yet. How much does she drink at each feed? If she's really only taking a couple of oz at a time then you might want to try a different formula.
Our dd hasn't 'drunk' milk since she had a terrible snotty cold at 13 months old. She literally couldn't suck the bottle and breathe so refused. We tried everything - beakers, cups, you name it! Nothing would persuade her to drink milk after that.
All we could do was put milk in everything we could - porridge, mashed potato, cheese sauce etc. We offered hot chocolate and she would sometimes eat cereal and drink the milk in the bottom with a spoon, but she has never had a drink of milk since (she's now 3.9).
I thought she might try it at nursery as they offer milk or water but she always chooses water. She rarely has squash though and never milkshake.
We make sure she gets lots of yoghurt and cheese - what else can you do????
FWIW she's healthy and thriving - a little on the chubby side if anything
Remember, you can only do your best - as parents it's our job to provide a healthy diet - we can't force them to consume it!
Try adding milk to lots of foods, eg porridge, fruit, more or less anything, grate cheese into meals and add plain yogurt to things, too. Have you tried getting her to drink from a cup? Squash isn't very good for babies' teeth or nutrition (lots of sugar); I'd have thought milkshake powder was pretty sweet as well.
She went off it at 4mths so started weaning and she loves her food and drinks plenty weak squash. She is a perfect weight but apparently needs 18oz baby milk a day which she hardly does. She might have about 8oz. I even tried putting milkshake powder in it to improve flavour. I'm worried she's not getting enough nutrients, any ideas? Thank u