Am I wrong for not correcting my daughters behavior when she slapped her mom when she found out that her mom cheated on me?

This happened last night, it was 48 hours after D day. One of my family members let it slip to my 16 year old daughter that her mom cheated on me with her boss. I refuse to lie to my children so when she asked me if it was true I confirmed it. When mom came to pick her up from our home (I had kicked her out about a day ago) my daughter slapped her mom across the face hard and said "how could you, I'm staying with dad" and went to her room. The soon to be ex wife started yelling at me asking why I would poison her against her. I flatly explained that I had not told her anything, our daughter came to me and asked if it were true, and I confirmed it. My soon to be ex demanded I punish her. I told her I would talk to her about it, but no punishment would happen, I explained that this was the consequence of her actions.
Updates
9 mo
After mom left I told our daughter that hitting people was never acceptable. She asked me if I want her to apologize, and I said when she is ready and not angry yes. She asked if I want her to go with her mom, I told her that it was her choice.
Am I wrong for not correcting my daughters behavior when she slapped her mom when she found out that her mom cheated on me?
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