Ok, so I just had a thought!!!
One of the few things that has stuck with me about the mid-season finale is Rowena's reaction to when they first told her it was Lucifer they were going after in the cage. They showed her reaction and then they showed Dean reacting to her, implying that there was some significance some where. But, the whole thing was very subtle and low-key. Regardless, I can't stop trying to analyze it because there's something about it I just can't put my finger on. Because if you take her initial "squee" reaction and pair it with her behavior at the very end, when she's walking down the stairs with Crowley (she's so sure of herself...), there's something that just doesn't add up.
And then I just had this thought: What if it was Rowena, the whole time, sending Sam the visions?? And when they all finally came to her and told her their plan, she squee'd because her visions/attempts actually worked.
I don't mean to give her character too much power, but surely if she can create a spell to control an angel, she can implant visions into Sam's head.
As for her motives, I don't know yet. Obviously they have something to do with Lucifer, but if the visions (and the failed warding in the cage) were actually all Rowena's doing, then it would surely explain a lot about her behavior throughout the whole episode.