Should I ask?

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Should I ask my professor to change my seat? I feel like I'm being rude by asking to move seats because the girl I sit next to is overweight. In my music class we sit in an auditorium. The girl that sits next to me is so sweet but it's like she's sitting on top of me. I can't take notes in class because my table pulls out on her side to mine and pushes into her stomach. I just feel bad because she's so sweet but I feel like we are both very uncomfortable. What do I do?