Do I lose my half of the money I paid in taxes or does the ownership switch for me and her to me and the person who acquired it through tax sale?

You would stand to loose the monies you spent paying your halve of the taxes. If she is failing to pay her share of the taxes, then you could pay the entire tax bill (keeping a record of course) and/or you could ask the Court to enforce the order and make her pay her portion (however, there is a limit to this type of enforcement). Once the property goes to tax sale, the highest bidder will be awarded the property. Which one of you pays your yearly tax bill is not the concern of the tax office, and they don't care who the Court told to pay; they will call for a tax deed sale for any owner of a tax certificate for that property who has held such a certificate for two (2) or more years.