How to react when your ex has sex with a new person after 2 weeks of a break up?

We were in a relationship for 3 years. We were in the same city for half of it and later it turned into a long distance relationship. After 3 years she didn't had time for me cos she got employed and asked if we can end it.
2 weeks after the day we broke up she hooked up with a guy she found on tinder and had sex with him.
I don't know how to feel now. I feel betrayed but I can't blame her cos se says we broke up.
But is 2 week enough to get over a 3 year old relationship?
How to react when your ex has sex with a new person after 2 weeks of a break up?
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