Mobility car for elderly on attendance allowance help!

Hi everyone. I’m new to the forum! I’m a carer for my elderly mum. My question is that she is on attendance allowance, the lower rate although her condition has worsened and so she is going to apply for the higher rate. Firstly, anyone know how to do this? The reason though for my post is that I take mum to all her appointments at hospital and drs but my car has just packed up! I can’t afford another car and she could do with an adapted car for her wheelchair and easier access. I spoke to mobility this morning and they said attendance allowance isn’t a benefit that allows a mobility car. Mum cannot use a bus! Taxis would be difficult too! Anyone know if I’m missing something here? She’s already had to postpone her 2nd covid vaccine today until I can sort something out.
Thanks in advance for your advice!