Is deleting an Apple account allows to reset the phone?

My sister died last March and I have a hard time to reset her iPhone for my dad to use cause I don’t have the purchase receipt. I don’t need access to her images or info since I feel it’s personal. In her will, she pointed my dad as the one to inherit her and I have a court order.

Apple don’t allow me to reset the iPhone without a receipt. If I ask

them to delete her Apple account, will I be able to reset her iPhone for my dad to use? It’s a new iPhone and now it’s just sitting dusting while my dad does t have a good phone. I’m so exhausted sending requests for reset and being ignored just because I don’t have a receipt. I have a court order recognizing her will and point him as her sole inheritor.