Taking less formula

[HuskySnow]

My baby is now 3 and a half months old, and was born 9 weeks early (she should only be 6 weeks old)
She has been taking between 90ml and 120ml every 4 hours during the day and going about 6 hours at night, but lately she has been taking alot less formula than normal. For example last night she woke up at 3am and then 6.30am and took only 120ml combined at both feeds. She's growing and getting bigger all ok.
Is this normal? Will babies just take what they need?
I'm just worried as we spent 6 weeks on neonatal unit and really don't want to go back (I might just be over thinking it!)

Does she take more during the day to make up for the smaller night feeds? Are you using a teat suited to her age? (might need a faster one). As long as she is putting on weight it should be ok. How much does she weigh and how much milk is she taking in 24 hours?

I tried the teat size up a few weeks ago and it was too fast, though could try again now.
From about 2pm she takes alot more, and in the evening drinks way more than during the day. She was weighed last week and was 9lbs 4 which is on 50th centile from her due date.
Yesterday she took just under 600ml in the whole day.

A general rule of thumb is 2.5oz per lb of weight so 9x2.5 = 22.5oz = approx 675mls. Her intake sounds ok. Maybe she's working towards dropping the night feeds