2 pointsSorry to hear about your grandmother. Let me check I have this right, you are the granddaughters entitled to 12.5% each of your grandmother's Estate? Who is the Executor(s) of your grandmother's Will? Is her house the major part of her Estate? Who lived in it before she died? Your grandmother on her own? Who is living there now? Is it unoccupied? Is it still furnished? What, if anything, does the Will say about selling the house? Ignore what your Aunt's Will says. It's irrelevant to your question, and anyway she could change it.
1 pointHeard a similar story from a colleague and yes, the "lodger" claimed of being the boyfriend by organising and paying for the funeral. Dogs chipped in both names supported his story. He still lives in the house, rent free now. Tell your aunt to put something in writing and attach it to the will. I would do this in front of a solicitor, it would cost peanuts compared to the potential trouble ahead.
1 pointHere is a link to guidance. 44045 seems to be the part. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/794990/dmgch44.pdf