A fair way to split is to base it on a ‘per share basis’.
Costs of selling split 50-50, that’s fair. A joint cost.
Based on the original cost of the house you divide the original cost of the house up based on your input. So on a 100k house (including the buying fees etc) she put in 10k, you put in 5k. That’s 10% for her 5% for you.
After you sell the house you divide the final capital amount by 15, you get 5 shares she gets 10.
You didn’t mention who paid the mortgage. If you paid equally then no need for further adjustment. If you paid it all then you could rightly add some adjustment to your share.
Its not about winning its about a fair financial settlement especially in such a short marriage. This method is at least transparent and open. Suggesting 50:50 or 2-1 etc has no legal basis. The wording is ‘a financial settlement that both parties agree to’. Try to have an amicable split it will help you and her heal and move on.