Cows milk

My baby was drinking 8oz of formula at night before bed and when I switched her (just switched with no transition) to cows milk she only takes at most 3oz before bed. This is the last 3 nights. Is this normal? I don’t know what I’m doing. Should I put her back on formula and slowly transition instead. 🥺😅 what do I dooooo?! Does she hate it? What would you do if you were me?