Emily,
7 year olds go through this rough stage of yucky language. They try out tone and be very aggressive. (I think their minds they are being assertive.) My daughter is coming through this now. She's on her way of this phase I suspect. Additionally, she takes a nap most days on the way home from school. That has decreased this year, buy historically she has slept all the way home from school (35-45 min. drive). She hadn't been sleeping for the last few months, and now she's back to sleeping. I chalk that up to a growth spurt coming or in the process.
Hold firm to what you believe in and expect from you daughter, but also understand what is happening and articulate that back to her. When my daughter is filled with tone and demands, sometimes I restate what she said as a question, "I'm sorry. I didn't really understand. We you trying to ASK me to move over so you could......" When I get a confirmation, I ask her to ask again.
We also do a lot of talking on the way home from school and at bedtime. At these times, I often hear about who has "been mean" and how hurt she is feeling. We talk through the school social dynamics. I ask how she might handle the situation next time. She's finally coming to the place where she says, "I can stick-up for myself." She's even asked to role play. Yeah.
Check in with her about what's happening in her life. We have found more pushing back at home and tone when she is feeling powerless at school. Yes, we're talking to the school about it.
Good luck,
Stephanie