...or is she trying to turn around or sit up on the changing table?

When my big girl (now 3.75 years old) was around 10 month old, she started to stand up and showed the same behaviour like your daughter if I had tried to keep her down. After she have had learned to walk, she stopped it again. Now my little boy (13 month) starts the same. I think it's a phase, which ends.

To cope with it, I change/changed them standing up and using Pampers EasyUps instead of normal nappies. This is a little bit complicated, if it's really dirty, but in general it works fine.

I'm a big fan of assuming this stuff is a stage. She's mobile now and probably frustrated with being imobile. After a while, she will come to know it's unavoidable. I am also a big proponent of talking to them. She may not understand what you are saying but the tone of your voice will probably be reassuring. Good luck!