Toilet refusal 4 year old

[Luolabell]

Hi, I’m totally at my wits end and don’t know where to turn. My daughter has been potty training for nearly 2 years, she was fully potty trained at nursery but refuses everywhere else. She will only wee on the toilet with a nappy on (the bottom will be ripped out of the nappy). She won’t wee in a nappy unless it’s on the toilet and she knows when to go. She’s now started school and is refusing to go and holding it. She’s had 2 UTIs from her toilet issues and holding which I think is contributing. I just don’t know what to do anymore I feel like such a failure, and now so concerned she will get another UTI from
holding all day at school

This is difficult but I’d start by saying no more nappies. Throw them out. Put a change of uniform in her bag for when she inevitably wets herself at school and let her deal with the natural consequences. Same at home. It should have got this far really. She should never have been allowed back in nappies after being potty trained at nursery.