A common theme is survival. The 'dead girl' often has to find ways to stay alive in a world full of walkers. Another theme is identity. Since she's in this strange state of being, she has to figure out who she is now.
Another possibility is Draco Malfoy. He was always in a difficult position, being from a Death Eater family but having some doubts. In this fanfiction, he could be in a situation where he's made some bad choices and now feels like he's a 'dead man walking' as he tries to find a way to make amends or escape the consequences. He has to walk a very thin line between life and death, both literally and figuratively in the wizarding world.
The tone can be different too. The original 'The Walking Dead' is mostly about survival and the dark side of humanity during a zombie apocalypse. But 'the walking dead lemon fanfiction' might add elements of humor or different kinds of relationships that are not as prominent in the original. For example, there could be more light - hearted moments between characters that contrast with the overall grimness of the show.
One interesting 'Dead Girl Walking' in 'Walking Dead' fanfiction could be the one where the character has a unique survival strategy. In many such fanfics, the 'dead girl' might be a new character who brings a fresh perspective to the post - apocalyptic world of 'The Walking Dead'.
Michonne does die in the comics. The circumstances surrounding her death were quite dramatic and had a significant impact on the story's progression. It happened during a major conflict with other characters.