What angle was her seat at? Kids with good head control don't need to be at the full 45 degrees anymore. A tech "checking"
dd's
Marathon when she was 20 months put it at 45 degrees, and she had a fit because she was tipped so far back she couldn't see out. She should be able to go as upright as 30 degrees (IF her neck strength is adequate, and IF the car seat's manual doesn't forbid it), which could make a big difference.
Lots of kids seem to protest the car seat in general at that age anyway. My dd did at 13 months, and again at 16-17 months. It's not that they don't like rf, since they don't know any different, it's more that they don't want to be restrained.