He has never seen her cry.
He's seen her angry many times. Frustrated often. Dogged and immersed into cases to the point of oblivion. He'd heard her curse, shout, and he's seen her so calm it almost scared him. But never had he seen her cry.
So when he enters the locker-room, the sound of sniffing filling his ears, and the hunched over, trembling form of his friend meeting his eyes he doesn't know how to react.
When she's angry it's best to just let her vent. When she's frustrated it's best to offer a cup of coffee and carefully ask if there's a way to help her. But when she's close to breaking? He doesn't know how to deal.
His heart tells him to hold her. His brain tells him to give her space.
Tentatively he sits down, waiting for her to take note of him. And when she does, her face tear-stained, her eyes red and pained, he know there's only one thing to do.
Gently opening his arms he breathes a silent sigh of relief when she falls into his embrace and lets go.