My mum often tells me that I refused milk from 8 months on - I actually picked up the bottle and threw it at her.
She started giving me milky tea (I have a massive tea addiction now but I'm well hydrated) could you try that?
idk Hope - have you tried getting a dietician referral for some professional help, if she has dropped more than 2 centiles and is still dropping it is cause for concern.
All i can suggest is get as many different types of cups etc in and let her try them all - have you tried a cup with a straw, or a doidy cup to get her drinking more fluids?
Aaron is off his milk at the moment, but is still carrying his steroid weight so I'm not too worried. He only took 3oz this morning and I made him some very runny weetabix with another 3oz