It's always difficult to try to help a woman who's crying. So people fall back on cliche questions or comments to try and get us to stop. As helpful as you may think they are, sometimes they can make things worse.
"Are you crying?"
Literally the worst possible thing you could say. It makes her feel embarrassed and ashamed of showing her emotions. If you think she's crying, odds are that she is. When in doubt just go with that.
"Don't overreact"
To you it may seem trivial and quite frankly stupid, but it is obviously upsetting her so just sit and listen.
"Calm down"
Just never say this to a woman in general. No matter what the circumstances.
"Tell me what's upsetting you"
This may seem sweet, and I really do believe it is. However, sometimes us women just need someone to hold us while we cry without talking it out. That time will come, but you have to be patient. Instead, substitute this phrase in for it: "I'm here for you, and I'm ready to listen whenever you're ready to talk."
"What's wrong?"
Sometimes we don't know. It's also hard to tell you what's wrong when we are sobbing hysterically while being unable to breathe. If you're an ugly crier like me, you know the struggle of trying to talk while crying and being completely incomprehensible. We might as well be speaking gibberish. So just give it time. She'll open up eventually.
"Don't let it get to you"
Again, this is a phrase that means well but isn't helpful. We can't help what "gets to us" and what doesn't. We have emotions that tell us how to feel, we don't always get to control them. That's just one of the joys of being a woman. Embrace it.
The most important thing someone can do when a woman is crying is just be there. Simply hold her and tell her you're there. Let her know that whenever she's ready to talk, you'll be ready to listen.