How to comfort your crying girlfriend?

My girlfriend feels bad she thought today was her favorite rock stars wedding anniversary but she thinks she has the date wrong she feels stupid. She really loves him she's obsessed with him also jealous that his wife is young and beautiful she's not. She feels stupid for getting upset over nothing she said on his Facebook it says his anniversary is today but on Instagram from his past posts it says tomorrow either way she's gonna be upset about it. She had a really bad breakdown this morning over him she knows she'll never see him he lives in another country he rarely comes here. How can I calm her down? What should I say to her?
How to comfort your crying girlfriend?
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