My daughter is addicted to Minecraft?

So my daughter gets $150 every two weeks, so pretty much $300 a month. But she only spends it on Anything that has to do with Minecraft. Like her whole room has minecraft or something in Minecraft on it. Now most people would say its just something she really likes so I should let her do it. Except this affects her whole life. 3 years ago when her Friend showed her Minecraft, She had good grades. A's and a few B's. Now though 2 years later, She will barely pass 7th grade. She now has D's and F's. Instead of actually doing the work she draws Minecraft characters or talks about Minecraft. Also at home she will sit at the dinner table and play MInecraft and not eat. Then in the middle of the night she will go and snack on Twinkies and Cupcakes. This is affecting her BIG TIME and its becoming a huge concern.

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