I'm not sure where you live and what the local laws are but where I am if both people are on title then both signatures are required to list a property for sale and to sign any subsequent sales contract.
You can't stop her from smearing you and I wouldn't waste any time defending yourself against her attacks. I know it's frustrating and you feel the need to defend yourself. Coming from personal experience, it really isn't helpful. People are going to believe what they will. How you conduct yourself is a reflection of your true character and is more important than what your wife says about you.
I agree that her sense of entitlement is overblown, unless she is the sole owner of the property, she probably can't sell without your approval or the court's order.
There's a statement often made here, don't let your ex be the one giving you legal advice. It is sure to be biased against you and intended to discourage you. Get the real thing from family law attorneys or solicitors.
You have to be a virtual angel, you already know she will frame you to overreact and record it. (Hmm, if you can record, then I would expect you can do the same. However, historically courts have avoided listening to recordings but the agencies and professionals who work around the court probably can. I've viewed it as a special type of insurance, a way to protect myself from some of the allegations, and having proof I am not the one behaving poorly helped me sleep a little better.
As for her smearing you with libel, slander or even allegations, you do have to defend yourself in the legal scenarios. If it does go legal, never make plea deals lightly, they usually are a way for perps to admit 'less' guilt in exchange for court to move on to the next case. If you're not guilty of anything bad, then don't plead guilty to lies.
However, JM's advice is generally sound if it is dealing with smearing that does not involve legal action. This is probably "sour grapes", Blame Shifting, perhaps trying to make you look worse than her. You may have to respond to certain claims but be careful not to be seen as bickering, tossing spitballs at each other. She may act like a three year old but you need to weigh your actions and reactions judiciously.