Robin showed up in the middle of Anna's torture. They'd pushed her past her limit. She held on, as best she could, to the physical form she felt so attached to. But that was just another thing for them to use against her. Anna was pretty sure that torture in Hell wasn't as bad as what they put her through when Cas let them take her. But that wasn't the worst part. The worst part was that they kept showing her what they did to Cas, how they'd tortured him not long before he turned her over. And this, they said, was her fault. They blamed her for Castiel's disobedience. When he turned from them, they made it all the worse on Anna. She was there for months, ripped apart by them, body broken, heart broken, and spirit screaming for release.
It was seeing Robin's living room that brought her memories back, a bit anyway. She was disoriented, full of pain, still holding wounds here and there from he siblings. She darted here and there, moving to the first place she could remember seeing Cas and moving on. Screaming for him. She hit the lake first, then the pool, then her old room. And finally it hit her where he was.
Anna landed in the living room with a thud and a roll, knocking the couch over and skidding it across the floor. "CAS!" She practically ripped open Sam's door, tripped as she rushed into the kitchen and then stumbled up the stairs. "CASTIEL!"