My sister got my mum to cut me out of her will. My solicitor says I can protest it once mum dies?

Yes you can. I hear that happens all the time when some is disinherited. A will is not what many people think it is. It's not the final say. It's the final request.

There is no application for Durable Power of Attorney. You father has to assign someone. He needs to assign Mom, you or sister. Actually Mom is not considered next of kin, they are married but not related. DPOA needs to be gotten before the person can no longer make informed decisions.

The only thing your sister can do is file for guardianship.