Welcome to the boards
Possibly sounds like she has here day/nights feeds mixed up
have a look here (1st post from SKibbit) and tell me what you think
https://babywhispererforums.com/index.php?topic=57221.0 Do you think she could be teething at the moment? That would also make them take less milk as the sucking action hurts.
Have you tried giving milk in a sippy?
Waiting 5 - 10mins and trying again?
Is she still taking the same amount of total oz's in a day/night?
Putting rice cereal in her milk won't make any different (except maybe clog the teat), formula is more calorific then baby rice.
Can you post your routine and amounts she is taking? Are you on a 3 or a 4hour EASY, if you are on a 3hr EASY this may also be the problem, in so much as she isn't hungry after 3hrs and would take a full bottle at 3.5/4hr.
Let me know
Lauren