I need some parenting advice 😩

My 4 year old is on the spectrum. This makes it really hard for him to regulate his emotions. Obviously all kids have trouble with that but when you’re on the spectrum it’s definitely harder.

He’s been doing a lot better but some of the things he used to do was scream cry if something happened that was an inconvenience like a fly landing on him or having trouble putting a shirt on, dropping something etc….. it was a really big problem. I sent him upstairs once to brush his teeth and he got up there and screamed bloody murder so bad I thought he fell and cracked his head open.. but what was actually wrong was that his sister moved the toothpaste to where he can’t reach it

Like I said, he’s been doing a lot better. We’ve been working with him a lot with being more calm when something happens. He can actually fall down now like a normal kid and get up and brush it off instead of screaming bloody murder which is amazing!!!!!!!!

What I’m having trouble with is that now as he’s losing those bad habits, his 6 year old sister is picking them up.

When she doesn’t get what she wants or is just mad in general, instead of calmly talking about it which is what she would usually do, she has started clenching her fists and shaking ridiculously because she’s so mad…. Something she picked up from her brother

Pretty much everything that her brother does behavior wise because he’s on the spectrum, she’s now copying when she’s upset about something.

It’s hard to teach her those actions aren’t okay when her brother can’t help it. And it feels wrong to tell her sternly that she can’t do the things he does when we don’t give him those same reactions.

How do I go about this?!