Help me to keep my Home

I realize that there are, and am greatly respectful to the far more important causes out there than mine. However, I know that there are, no doubt, plenty of people out there who may have had to go through what I am currently going through and may have the means to give a little to help my cause. I used my life savings, a few hundred thousand dollars, to purchase a property in 2013. I was in a relationship and, unfortunately, her name is on the Sale and Purchase Agreement to. I was foolish and I did not protect myself even though the lawyer recognized the significant input I made versus hers. We split after 2 years of owning the property. I have offered her back everything she put in plus a percentage of the Capital Gain based on the percentage ownership she had in the house. This has been rejected. She is going for 50% of everything I have. The property is in Auckland so the incredible rise in property values has lead to a potentially crippling amount of money I would have to pay to buy her out. I would sell and move away from Auckland but my career is here. There are no children involved, we were not married or engaged but she is claiming we were de facto under the Property Relationships Act. She is now demanding around $400 000. I am fighting it legally at great cost to myself and watching the value of the property increase daily, which sounds good, but just means the pay out to her gets larger and larger everyday. If anyone out there feels my pain, and is able to help, my appreciation would be beyond words. Thank you.