Gift or repayment?

My sister and I jointly owned two properties and six years ago my sister lost the first of the properties when she used it as security for a loan. She didn't ask me before using the property as security, but we didn't have any prior arrangement in place to deal with a situation like this. She had lot of personal problems at the time and there is animosity between us but she would now like to give me her half of the second property. If the properties are of equal value, is the transfer of the second property treated as a capital repayment, with no tax payable? Or does the lack of prior agreement mean that it is treated as a gift, with a certain amount of tax now due?

Hi,
If she has not lived in the 2nd property this would be seen as a disposal so capital gains would be due on her share.
Thank you.