Recently diagnosed 8 year old - need advice on strong emotional dysregulation.

I have 4 kids ages 3, 5, 8 and 12 years old. My 8 year old was recently diagnosed ADHD (tested her and my oldest at my request by her pediatrician - surveys done by me and 3 of her teachers) and we had to force her school test her for a suspected Learning Disability.

The school psychologist did a battery of tests and discovered issues with executive function, slower processing speed, confirmed ADHD, and also discovered a learning disability affecting reading and math fluency. She has an IEP now that we just got at the very end of the school year (literally days before the end of school) that will take effect at the beginning of this coming school year.

My daughter goes to a Montessori school and is in a combined 2nd/3rd grade class (she'll be in 3rd this year). Her teacher is also recently diagnosed ADHD.

And I have ADHD that I have literally JUST begun medicating for the first time in my life at almost 40 years old and we haven't gotten it all dialed in yet for myself (I was diagnosed at age 6, just never medicated or treated before the past couple of months).

I was a little shocked my 8 year old came back as having ADHD and not my 12 year old - but I think my 12 year old just masks better at school. But I knew my 8 year old has had something different going on with her since she was very young.

She has ALWAYS been quick to anger. She tries VERY hard to control herself now but she literally is incapable of doing so if pushed too far. And with 3 siblings and a short fuse - 2 of whom like to push buttons, that happens a lot.

She just went into this monologue tonight about how she hated being the middle child and why, and used the work hypocrite correctly, more than once. She explains her feelings better than most people are ever capable of, but she cannot control them.

I also discovered she's trying to hold it all in, but I explained that it's ok to get it out, it's better and healthier to get it out, just in ways that don't hurt other people or ourselves.

She has a really hard time with friends bc she is very picky but also, can be mean when she is angry. Usually she is so sweet and kind and loving, but if pushed she can get mean.

Frequent mental breakdowns, total meltdowns over sensory issues - especially uncomfortable feelings like a rock in her shoe, her sock seam, being itchy especially at night.

Is this all ADHD or should I keep digging? I know everyone's experience is different but I feel like there is something more going on.