To go off the feeding schedule?

When she was in nicu she fed every 3 hours at certain specific times with 30-35b ml plus whatever colostrum I produce.

But now 5 days later her feeding schedule varies.

She’s starting to want to eat frequently now every 2 hours with whatever amount we accidently give her (usually 35-40ml) and breastfed before bottle formula whatever she eats until pediatrician approve of her breastmilk only diet.

Is it okay to just feed her whenever she roots or cries instead of going with a schedule?