Autism or just a crappy mom?

Hi, I’m in the process of trying to get my 7 year old daughter assessed but it’s so overwhelming. I genuinely think that she’s on the spectrum and needs more help than I can give her. I have read self help books, tried different strategies at home, made a conscious effort to model self regulation and most days it doesn’t seem to help. She currently is in speech therapy at school but it’s pulling teeth to try and get an assessment for autism. The school is trying to say that because she gets good grades, she doesn’t raise any red flags. But as soon as she is home, it’s meltdowns and impossible to get simple tasks done. I feel like the world’s crappiest mother since I can’t help her. She’s a great little girl and I love her very much but I’m so incredibly frustrated because I don’t understand why she can’t/wont do simple tasks and instead melts down into a screaming/crying mess. For example, this morning before school I reminded her that she needs to brush her hair and teeth. She screamed gibberish at me then started running around the house going “meep meep meep” and trying to hide. Finally I got to her and forced her to sit in a chair. She became a huge crying mess once that happened and I felt like the shittiest mother for making her cry. But she needs to understand that in life, we have to take care of ourselves and brush our hair and teeth. I’m not asking for her to do more than just the basics of self care. I’ve tried making charts that help show the process of getting ready every morning as well as incentivized reward charts. Some days she’s “normal” and pleasant but other days she becomes a wild child doing jibberish and flailing her arms at me. I’m so overwhelmed and alone in this. I want to help her but I don’t know how. I looked forward to being a mom so much but everyday it just feels like I’m ill equipped for the job and that she’d be better off without me.