Out of interest, how old is your sister, if she is too old now to get a mortgage, why would she be even considering emigration in five or six years time? Emigration is a huge upheaval for any family especially so for parents getting on in years. It looks like your sister us burying her head in the sand and can't face moving from the home she has become accustomed to living in these past number of years. Hope you come to an amicable solution OP, it's very important to try and preserve the relationship between the two of you.