My girl does when she’s really excited or just feeling lots of emotions :) she’s 2 and I find it completely normal for her age
My son is 2 and he slaps his hands and arms sometimes to pretend he is flying or mimicking an animal that is flying
My son flaps his hands when he’s super excited or scared about something. But it’s not a daily thing. He’s 2
My kid flaps hands a lot.. it’s nothing to be concerned but is a sign! My son does it a lot! He is doing it less but he still lines things up, talks a lot.. super duper smart
If that’s the only thing then no she isn’t. My 3 year old is autistic and flaps all the time but he also has every single other autistic trait and is non verbal. Your mil needs to pipe down
Yes it’s really common! I’m a children’s speech therapist and see a lot of children with Autism especially under5s. Handflapping alone is never a single trait conclusive of Autism. Lots of little ones do it - even my own boy did for between 1-2years old, they eventually stop and grow out of it.