I gave my sister and her two year old a lift home last night. My niece is 2 and I put her in my son's car seat which is the right size for her. She immediately started to struggle as I put her in it and cried. I calmly told her it was ok and that we had to wear our seatbelts.
My sister laughed and said "She never stays strapped in in her car seat. She can undo it now so she's probably upset she can't escape."
A bit of backstory, I was in a crash recently and although I have carried on driving I am definitely more aware that you can't control other drivers. Someone went in to the side of my car and then another went in to the back of me. DS was in the car too and thankfully was ok.
To get to my sisters you have to drive along a motorway and a few busier national speed limit roads with busy junctions. We started driving and my niece was still crying. I tried to distract her by putting music on but she kept saying "Out" and reaching for my sister.
She wasn't hysterical just a whingey type of cry. My sister then said "I can't leave her to cry. I'll loosen the straps so she can get her arms out." I told her not to because then she wouldn't be in properly and she could get hurt in an accident or if I had to slam on suddenly. At this point we were already on the motorway and this particular stretch has no hard shoulder. My sister then said "Ok I'll get her out and hold her then." Despite me saying no she did it anyway and I couldn't pull over or do anything. I told her how irresponsible it was but my sister just laughed and said "You'd better make sure you don't crash then."
As soon as I could I pulled over and told her to put her back in the seat. At no point did I shout or make a scene despite my sister raising her voice and using a few choice words. I refused to go until she did. She eventually did but then of course my niece was even more upset and was crying louder than before.
When I got home I had a nasty text from my sister saying that I am clearly in need of help following my accident because I overreacted and accusing me of being a judgemental bitch criticising her choices. She also said that I have no right to tell her how to parent her children.
I haven't replied but can someone please tell me if I've overreacted or if I was being unreasonable?