In the first hour of the season premiere — aka Season 10, Episode 1, "Seal Our Fate" — Callie was cold toward Arizona but still communicative. (OK, she only talked about the surgical patients in front of them, but still, at least she was making eye contact.)
But in Episode 2, "I Want You With Me," Arizona came back to the apartment she shares with Callie to find half of their possessions gone — along with darling Sofia. "Callie? Callie?! Callie!" screams Adulterous Arizona.
The next time we see Callie, she's running with Sofia back to Grey Sloan Memorial to grab her laptop, telling Meredith Grey (Ellen Pompeo) and Cristina Yang (Sandra Oh), "My wife is an s-l-u-t. Sofia and I are spending the night at a hotel."
Mer tells Cristina that they can't let her do such a thing. Cut to: Derek coming home to find Callie sobbing on his couch, having gotten clearance to crash there from Meredith.