It depends upon whether at the time she provided the financing, there was any agreement between the two of you that in exchange for the money, she'd get any compensation, reimbursement (e.g. the money was a loan), part of the value of the barn, etc. If there was an agreement, she can enforce it against you in court if necessary, such as with a lawsuit for the money you owe her. But if there was no agreement, she has no claim to the structure or for compensation: if someone voluntarily chooses to buy or pay for something for someone else (like putting a barn on your property), their voluntary choice to do so without an agreement for repayment, etc. does not entitle them to anything.