Switching bottle to cup

My LO is on formula. She drinks water perfectly out of her straw cup. I was trying to transition formula bottle and put it in a cup. She freaked out. Complete meltdown. I know it can take time. But whoah .. I got frustrated and upset .. just as she did. Any advice please?! 😟😟 I didn't think it would be such a hard transition. She gets 3-4 bottles a day.