Grandparent in denial over childs autism diagnosis

My son turned 4 in September and was just diagnosed with autism. I have known he was autistic for a while so I saw this coming.

Mil does not believe he is autistic. It’s fine, she can have her beliefs, but she is always harassing me telling me he “acts autistic” for all these made up reasons.

1. She says he is a “pandemic baby” (which he’s not, he was born 18 months before the pandemic” and the reason why he struggles socially is because he’s “never been around other kids before” (not true, he’s been in preschool since sept where he absolutely does not fit it, does not even acknowledge the other children, and before he went to preschool, we did so many things with friends with kids, beach park, he’s been around other kids before) also- my daughter is a “pandemic baby” and has much better social/ language skills than him. Also, he was delayed before Covid was even a thing. He was 18 months old when Covid started and at the time he was not talking, also not pointing and not pointing is huge ASD red flag.

2. My son does repetitive things. Will open and close doors for fun, puts things in and out of buckets over and over and over and over again. She says he does this because I “let him” which is true- indo let him because this is what he would rather do than play with toys.

3. He has meltdowns because I dont discipline him. His meltdowns are sensory overload. And no, I don’t discipline him when he’s in a distressed state. Like what the fuck.

All his delays are my fault. I didn’t disclipine him enough, he doesn’t talk because I didn’t read to him enough. Everything is my fault.

Can anyone relate? I don’t care if she believes his ASD is fake or whatever but I just don’t want to hear her anymore.