You have two choices. You have a mutually acceptable agreement for her to quit claim the property back to you entirely or you proceed to quiet title in court. For both of you the one that makes the most sense is to come to an agreement.
As I am sure you realize now, do yourself a favor and hire an attorney to draft the documentation if you come to an agreement. If you don't have a good agreement you will just have further problems.
As to your depreciation and benefits observations, those don't matter. This has nothing to do with depreciation or benefits. It is merely your agreement. Since you have no written agreement and don't appear to have an oral agreement you will have to agree to something now (which is why you have an attorney in the first place). Good luck.
This answer is for informational purposes only and is not legal advice regarding your question and does not establish an attorney-client relationship.
Mr. Murillo is totally correct. This is something that the two of you need to mediate between yourselves and see if you can come up with an agreement. The family law courts will have no jurisdiction over this and this is an equitable argument that would need to be resolved by a county court judge (due the to the money involved). It would be a lot cheaper and less acrimonious if you could work out an agreement and have an attorney help you with drafting up the necessary documentation. Good luck.
The information provided in this answer does not create an attorney-client relationship. If you are interested in his legal services, feel free to call Chris at (303) 409-7635 at his law office in the Denver Tech Center. All initial consultations are free of charge.