As there does not seem to be any trade or business for which these legal expenses are an "ordinary and necessary" expense there is no deduction
All business expenses must be made in the conduct of a trade or business and must be "ordinary and necessary" of that business activity.
for a more detailed explanation.
From what you wrote you are not required in any way to pay her; but that you feel some moral or ethical obligation to pay her part of the proceeds because while she was stopping you from making the sale the value of the property went up. I would assert that she is not entitled to any share of the gain since it was her intent to harm, and not help, your efforts to sell. From the description, it seems highly doubtful that you would have been able to recover any decrease in value that could have happened during the litigation; so, the fact that you were blessed with an increase in value is not at all of her doing and she should not be paid in my opinion.
Depending on all of the facts and circumstances there is a slight chance that the legal expenses might qualify to be deducted as an investment expense. You would have had to bought and maintained the property as an investment (and not for personal
use) and the expenses would have to be for the production or preservation of that income
For more details on investment expenses see the article at http://www.irs.gov/publications/p550/ch03.html#en_US_publink100010270
If you want to pursue that chance you will need to discuss all of the facts and circumstances with a tax practitioner to see if it may apply. Unfortunately this forum does not allow enough information for me to be able to give such advice.
I hope this helps to know that the legal fees are not a business expense and are not deductible
on that basis and that although likely not able to be deducted as an investment expense that possibility can only be ruled out by considering all of the facts and circumstances in your case. From what you were able to tell me it seems it was a personal decision and therefore a personal expense to have the woman on and get the woman off the property.