D'aww and Jojo will have her hands full with Alex, and Clary will either disappear right before Billie comes back or right after, so she's going to be drained and trying to deal with Logan. And Billie will look at him, kind of unsure of what to say, but she will hug him. "I missed you."

And once Billie realizes what's going on she will not take it well. Because I see Darren approaching her once they know that the new blonde is her.