My mum is undiagnosed but every ASD box I tick, she could tick twice, plus a few others on top. I am very sure she would be diagnosed, were she assessed.
And she said to me that she did try taking me to toddler groups, but since neither I nor she enjoyed it very much, it didn't become a regular thing — she'd go back and try a few sessions every so often, to see if I still hated it 🤣
But the good thing about having a (still undiagnosed) autistic mum as a (then undiagnosed) autistic kid was that, at least within my family, I wasn't weird, and she was on my side and had a good idea what I needed without even having to think about it.
Didn't like toddler group? Okay, neither did she, we'll do something else.
Starting to read at two and an obsessive reader from that point? Aw, just like her mum 😊 isn't it cute? We'd better go to the library so she's got plenty of new stuff to read.
Can't tie her hair back/do up her shoelaces/tell the time/brush her own teeth, despite many attempts to learn, until years after most other kids manage it? She'll get there at some point, no fuss made, keep trying but make adjustments in the meantime.
Can't bear tight shoes on her unusually wide feet? Okay, we'll get her the same shoes as last time, or spend two hours in the shop again finding bearable ones, and school will be informed that she'll be wearing trainers for PE instead of the regulation black plimsolls. (Not asked, informed. With things like that, my quiet, polite, unassuming, gentle mum would simply and confidently inform the school of the exceptions they'd be making for me. Same goes for my -6D prescription goggles for school swimming, when goggles weren't allowed, and my digital watch when only analogue were permitted. And the school just accepted it! I'm not sure how she did it… maybe it's your "mama bear" energy.)
I did also have major behavioural issues that they really tried hard to tackle, without any modern knowledge of ASD (though my mum did have a special interest in child development in general and autism in particular in the 80s
), and primary school did eventually go completely tits-up for me, but for "weird" things that weren't that weird within my family, where adjustments could be made without impacting others, my parents just kinda went with whatever kind of developmental paths I seemed to be trundling along.
If it's at all possible for her (I don't know what her difficulties are), I'm sure your DD either massively appreciates you, or will come to do so.