Sam liked Jo right from the off, but hesitated about making any 옮기기 because she was so obviously 더 많이 interested in his brother.
When Meg possessed Sam, she noticed his interest in Jo immediately. That was one of the reasons she eventually targeted Jo, after killing a 랜덤 hunter wasn't enough. If she couldn't force Dean to kill Sam, she was at least going to do her best to hurt them.
After Born Under A Bad Sign, Sam wanted to contact Jo to apologise. He phoned her, but before she could answer he hung up because he doubted she wanted to hear from him then.