I took my 7 month old to the states a week after the restrictions on liquids etc were brought in and it was very confusing and inconvenient. I would check with the airline what they allow you to take on board as there are still restrictions and different airlines seem to have different rules.
I took a few cartons of sma just in case I couldnt get fresh milk, I would also take a few jars just in case too. I dont know how old your baby is, what she's eating etc - but some biscuits etc to chew on are useful and easy to carry. And dont forget water or juice as it gets dry on planes and drinking helps to allieviate pressure in the ears when landing.
In my experience the cabin staff were great and were happy to help with milk and food etc.
I think its probably easier with a baby on a plane than a toddler who needs entertaining and wants to run round all the time!
Good luck and enjoy the trip!