Honestly, it is probably a control issue. If you are getting up and fetching multiple drinks for her each night when she demands it, she is controlling you. Give the child a drink before bed and then put her to bed. She will not die of dehydration before morning, I promise. She may cry and tantrum and who-knows-what-else, but stick to your guns and make her stay in bed without the drink. The tantrums and the calls for juice will go away if you remain consistent. You need to re-establish your parental control over the child. You are not being cruel or mean or overly strict or stern, you are being a parent. Your child needs a good parent much more than she needs a good friend.
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