Please consider the wording on the forms you submit very carefully.
Saying every day is like her worst day when that's not true is wrong. It's also very unlikely for anyone to have a neurodiverse condition that doesn't fluctuate day to day. The DWP and Tribunal are unlikely to believe a case where someone has the exact same presentation every day.
Once more, the Benefits and Work guides go through everything and deal with this as well. They are very good at showing you how to write your true information in a way that DWP/Tribunal can understand how difficult things are for your DD.
Does the PIP form suggest you submit a diary, so you can show how often good days and bad days occur? If not, do that, in accordance with B+W's suggested wording and back up every statement you can with reference to assessments, medical reports etc.
If she can do something, can she do that alone reliably, repeatedly, safely and in a timely manner? When you live with someone it's so difficult to explain their challenges, but you need to be able to do that to get a good result. For every question, assume the DWP know nothing about your DD and detail the difficulties she has with a task so they can see how and why she has difficulties completing (or even starting) it.
Despite my DD having indefinite DLA and asking for that to be taken into account and being fairly sure PIP would just carry on from that point, we were really put through the mill with PIP.
The Tribunal panel all agreed independently that DD should have been awarded the enhanced rate of both components of PIP on the paper submissions alone. She was awarded that with 'it is inappropriate to set a term' for the review, meaning it will have a light review 10 years later.
Some people seem to sail through a PIP assessment with hardly a blip and others have a dreadful time, all I can say is hang on in there and do your best 