My DD is 26 months old. She was with her dad and MIL today and decided to use MIL's car for short journey. MIL has a car seat in there which is a Group 2 car seat. DD is slightly below the weight requirements and my understanding is that these car seats (that use the main seat belt) are for 4 year olds plus?!!! My partner won't back down that he made a bad decision letting our DD use the car seat and that she looked fine in it. Should I mention to MIL that I don't want her to use seat?