You may need to 'buy her out' of her proportion of the property, either by use of cash or a remortgage of you do so.
Do you hold the property as Joint Tenants or Tenants in Common?
So the house must be held as Tenants in Common; you would be given the option to purchase her half or find a buyer for it. I would not recommend trying to sell as it will take time and may not net enough to fully discharge her partial mortgage.
A better option would be negotiating a sale to you of her legal interest of you can afford it.
Obviously my advice may change subject to sight of papers; if you want me to have a look at the deeds etc please send them to the JA email address marked for my attention and quoting this question. There would be a further charge for review of papers as, as I am sure you aware, this would be time consuming.
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