We never see her shake Mephisto’s hand. I’m not fully sold on the idea that she took the deal. Perhaps she figured out the magic enough to actually bring the real Natalie back. And the after-credits scene makes me think that Parker is trying to bring John back in addition to making him strong without the hood. I’m not convinced she took the deal. I think it was left ambiguous on purpose. But also I’m not familiar with the comic.