Perhaps I'm the only one to think the whole witch/Mami death scene was all a staged event to try to force the girls to seal their contracts?
The placement of the Grief Seed was strange. All the previous ones were in areas away from people (renovated room, abandon building, empty park) whereas this one was right on the side of a busy hospital. It also happened to be the hospital that Madoka and Sayaka frequent and have some attachment to. Kyubey certainly didn't do the logical thing and wait for everyone to stay together but instead suggested Sayaka separate and wander to the witch (where he could seal her contract if the witch attacked her). The whole talk between Mami and Madoka seemed to point toward her picking her wish sooner rather than later. That and Mami was the first one to bring up 'cake' in the whole episode, despite the world they were in was a mix between cake and hospital. After the witch emerged, Mami went down without a fight at all, leaving the two girls alone in a life/death situation. Life would've forced them to seal their contracts/death would be death... and who would choose death over becoming a magical girl? Also, Mami's attitude toward Homura kinda points in this direction a little but not much. Homura does say this witch is different than previous ones. I'm reading that as this was Kyubey and Mami's witch that they're using to put Madoka and Sayaka in a high-pressure situation to force them to seal their contracts.
But that was my impression, at least. Or at least that's what I wrote about in my blog. Idk, I won't be disappointed to see it was all real but that's not what I believe. Anyone else have other opinions on that?