Double Subverted: After that she comes back as a full demon.
Parodied: Alice gets a vase dropped on her head, Bob turns her into a dog to prevent possible brain damage.
Zig Zagged: Bob turns Alice into a demon to save her life, except Alice manages to pull through on her own, however it's because Bob only gave her the resilience of a demon rather than fully transform her.
No one has any injury that warrants such a treatment.
Bob's transformation spells don't heal as a side effect, and any new immunities or healing factor take long enough to kick in that the target will still die of their injuries or illness.
Enforced: Bob, Charlie and Dylan have already been turned into a werewolf, vampire, and ghost respectively, and for Alice to stay on their same Power Levels and keep up she needs to be changed into a demon or the like.
Lampshaded: "Great, I get a sword through my heart and now I can't go anywhere without cats hissing at me."
Invoked: "We need some way to mix things up between Alice and Bob, but romantic would be just too easy."
Exploited: Alice knows Bob has a spell that can save someone's life by turning them into a demon. So Alice proactively gets a Protective Charm placed on her that will keep her soul from being tempted with evil powers and/or sent to hell as a result of demonic conversion. Then she goes on a Suicide Mission knowing she can come out alive and more powerful.
Defied: Alice refuses to be turned into a demon, even if it would save her life.
Discussed: "So, Bob, about that 'Turn people into demons to save their life' spell... consider this my formal 'Do Not Resucitate' notice. Do Not Redemonate?"
Conversed: "Meh. This show doesn't really have any hot chicks." "Oh, just wait. Bob has a spell that can turn people into demons. My money is Alice gets an Evil Makeover after a near death experience." "Color me intrigued."
Deconstructed: Alice, after seeing she is a demon, becomes horror struck and soon after she loses all the qualities Bob saved her for in depression and self-pity.
Reconstructed: Right before Alice goes to the point of no return emotionally, Bob realizes what's going on and has a long talk with her, giving Alice only a stronger resolve to help Bob in his quest.
Played For Laughs: Alice practically forgets that she's a demon, and continues with every day life while ignoring the terrified looks she gets from everyone.
Played For Drama: The transformation keeps Alice alive, but alters her personality just enough to make her believe that everyone fears or hates her now, driving her to lose what little humanity she has left, and she becomes a demon mentally as well as physically.
Their heart is almost hit! Wait for me at Emergency Transformation and we can use the hell crystal to try and save them!