What do I do?

My parents divorced 10 years ago due to my mothers affair. A couple years later she had 2 children. She would occasionally visit us on weekends. But over time it became seeing my mother twice a month even though she only lives 15 minutes away. This year she decided to move back to mexico and take her new family with her. She is leaving tomorrow but she barely told me this morning. I dont know what to reply or feel. I wanna cry but im in class.