BLUF: Stop with the choices. You run the show.
If she acts like a brat, send her straight to TO. No negotiating, no explaining why. She knows why. When you call her out (after she's done crying, calm, and had some time to think), ask her why she was in TO. If she gets attitude or says "I don't know" defiantly, send her back. If she does say why, ask her what she needs to do to fix the problem and guide her to do so. If she refuses? Back to TO (and put her back in TO even if, when she realizes she's going back, she cries "okay, okay! I'll apologize. Nope! It's not a negotiation!). Lather, rinse, repeat.
ETA: I just wanted to add: I've noticed that parents usually do TO improperly. TO should be in a boring, out of the way location. No clocks or timers, no line of sight with windows, TV's, people, or anything. It should be a chair with a back that is not cushy, but not torturous to sit in.
There's no specific timeframe for TO. The "minute for every year of age" is BS. TO is for as long as it takes for the child to stop crying, tantruming, or lose the nasty attitude, plus 10 minutes or so to think and consider what they've done. Your mileage may vary.
When the child earns a TO, the parent simply says "Go to TO." Kids aren't morons. They know what they're doing wrong and don't need constant nagging and reminding. Telling the child to go to TO without explaining requires that THEY do the work and realize "Oh...I was doing _____." It puts the responsibility for their behavior firmly on their own shoulders.
There's no talking or coming out of TO. No "can I come out now?" No negotiations. YOU call the child out of TO when you're good and ready (which is sometimes helpful when you need to calm down yourself), and they come to you. You ask, "Why were you in TO?" And they respond. Nasty attitudes or backtalk result in a return to TO. Calmly taking responsibility for self results in them fixing the problem and moving on. Be sure that, if there is something you should forgive or apologize to your child for, you do so and them let it go. Forgiveness and apologies are important behaviors that we often demand of our children, but model poorly.
Hope that helps you!