Sharing of estate problems , advice appreciated

[kim123]

Upon my father's death in November 2015 my sibling and I made the decision to divide the main asset , our family home by me taking her house as part exchange for my Father's house so i could achieve a rental income . Only one valuation was obtained for my father's house which in my opinion was very much undervalued @ £160,000. I since had a survey on my sibling's property over concern on unusual cracks and it revealed unrepairable historic subsidence , with this report i backed out of our verbal agreement and the property sold in 2020 for £60,000 . My Father's house has been valued this year to the sum of £275,000 ( £115,000 increase in 5 years thus proving it was undervalued ) . I am now attempting to rectify this situation but my sibling now expects a contribution to half of the improvements made by her to my Father's house to the sum of £22,000 , she has lived there for 5 years and will continue doing so and these have been mostly cosmetic and unnecessary improvements and she is also sticking to one valuation again , I would very much appreciate peoples comments here as I have now lost a rental income and need the finances to buy another property in this ever increasing property market, also this situation was never put in writing