Sure, she set you up. But you told a lie and fell into the trap. She was wrong to intentionally set out to trap you, but you were wrong as well.
You don't have any control over her, but you DO have control over yourself. She was wrong and really should apologize to you, but you have no control over that. You can't correct her problems, but you can address yours. YOU were wrong and YOU should apologize.
Don't fall on your sword. Don't go overboard sucking up to make up for your error. Just a simple and honest apology. I was wrong. I'm sorry. Will you please forgive me?
Make sure that you ask her for forgiveness. That's VERY important. It puts the ball into her court. She doesn't have to answer you, but in her heart of hearts (assuming that she has one) she will know that she either has to forgive you or she'll have to justify holding this against you in the face of of honest, no-nonsense contrition. That's also the primary motivation for keeping it simple. If there's no hedging, no excuses, and no wiggle room, she can't dismiss it. Just make sure you're really sorry. If you're not, she'll know.
