Appointee letter and bank

[MemSahb]

I have a dd with severe autism, she is 26 and is in supported living.
I am her appointee from DWP to manage her benefit money.
I leave her bank card with the care home staff to do her shopping etc.
Today when they were hiring bolt taxi for her, the payment was blocked by the lloydsbank system and I had a fraud alert message on my phone registered with them, I couldn't reply in time " yes it's me" and her account blocked temporarily, they now asking to bring a COP but I only have appointee letter from DWP which they accepted at the time of opening the account however they now ask for COP.
I do not want to apply for COP unless its need by law as it has a fee and annual fee and annual reporting etc
The government site says
"You do not need to be a deputy if you’re just looking after someone’s benefits"
Why do we need to have COP if that's what government says?

My daughter has no language and severely autistic, she can't speak to bank.

What is the best solution?
How you all parent do this?
Any other solution to deal with a bank account if you are parent of a disabled person.

My other 2 children are also autistic but are under 15 and I will have this problem in future.

Please advise

TIA

Does your DD have sufficient understanding to operate a bank account? If not then just open a separate bank account in your name and get the DWP to pay her money into that account. That was what I did with my DDs disability benefits.
CoP for finances is only worth doing if your DD has assets other than her benefits. There is a fee waiver for people on a low income though if you do have to go down that route but as you say, doing annual reporting is a pain.