Hello and thanks for using Just Answer.
My name is ***** ***** am happy to assist you with your enquiry as my colleague is not currently available.
As your sister died after your Mum, the money she is to inherit from the house Sale should be paid to her Executor(s), who are then under a duty to add this amount to your sister's Estate and distribute it according to her Will.
I hope this assists and clarifies the position.
If I have helped, I would be grateful if you could rate my answer.