Not sure if this will help, but DD was diagnosed with ASD halfway through her second go at first year in uni (having failed the first year because executive function issues mean she didn't manage to hand in any of the required essays, and had a non-functioning day on one of her exams).
She's embraced the diagnosis, and has found her way to a tribe of neurodivergent people at uni. She's also got Disabled Student Allowance, which pays for a mentor to help her (we haven't seen much benefit from that so far, as she's spent a lot of time at home due to lockdowns, but she's hopeful that it will help a lot this year). In addition, she gets "special circumstances" leeway for deadlines automatically without needing to submit a form every time.
So, there are advantages to getting a diagnosis, even at this late stage, if any accommodations could help your daughter.
We paid for a private assessment, because we felt that with the way her time at uni was being affected she couldn't afford to wait for NHS (plus, her executive function issues meant I wasn't sure whether she was even on the list at uni - paying private meant we were in control of it happening). I realise that's not an option for everyone - it was not cheap.
There are a few fiction books which feature autistic main characters - I haven't read any of them, but follow authors on Twitter - so you could try seeing if she identifies with the protagonist, maybe? Geek Girl by Holly Smale or A Kind of Spark by Elle McNicoll both get mentioned a lot.