NSW Buying out siblings share of estate

I am the executor of my mothers will and we are going through probate. Myself and my sister are the beneficiaries. My mother has left us the house in NSW which has a line of credit account still owing for $70,000. We can't get the loan refinanced because of my sister's bad credit rating. I am entitled to 95% she is entitled to 5% (long story) after all debts are cleared.
I would like to buy her out so I can get the loan, I have already approached the bank and they are confident I should be able to get a loan. Can I buy her out? What would be involved and how would I start the process? To complicate things I live in New Zealand.