I'd talk to your dd to try to find out the reasons behind why she's saying she doesn't want her homework to sound like she's too smart.
*OR* it's possible it's just trying to "dumb-down" to fit in with peers, and that's the *only* thing that's up, then you can talk to her about how to be true to yourself and how trying to be someone you aren't ultimately doesn't work.
When I was able to get 2 seconds of DD's time away from Minecraft, I pulled out a bit of information. I asked a general question of both my girls after stating that across the US there was a problem with middle school girls "dumbing down", pretending to be less smart than they are - did they see this at their middle school? DD11 thought that was odd and said she hadn't seen anyone doing that. She left the room, and I noticed that DD10 was trying to get back on Minecraft (evading the question). She finally said that "maybe girls do it so other kids don't think they are weird." I asked if that happened at her school. After conversing about other people, I reminded her that
she had talked about changing her language arts papers so she wouldn't sound so smart.
Well, after lots of nudging and pulling, she finally said she was concerned about being seen as strange, but that she hadn't really noticed any taunting or teasing of anyone about being smart. She said she is just producing her regular writing and not altering it.
So, she is worried about being "weird". And, she is back to noting what makes girls popular (certain tee shirts and I don't remember the other stuff). Definitely some insecurity going on.