I included an autistic character in my comic, and so far it's been really fun and I don't regret it at all. A lot of ND readers in particularly find them very relatable, which feels really gratifying to me as an autistic creator, and NT readers tend to think they're a fun character whose unpredictable behaviour and blunt statements bring a lot of humour.
I think an autistic person in a zombie apocalypse story has a lot of potential because there's so many things you could do with that.
Maybe she feels guilty about the fact that in some ways the quiet, straightforward life in a post-apocalyptic world is kind of nice and she doesn't miss the noise or stress or social norms of the "world that was"?
Maybe she has a special interest that turns out to be the reason she's been so good at surviving, like she was a zombie movie buff or collected swords, or wrote detailed disaster plans in case of every possible emergency?
Maybe her high level of alertness and anxiety are really good for keeping her out of trouble?
Maybe she finds the disgusting smell of zombies very difficult to deal with and hates being anywhere near them?
Maybe the sound of gunshots is almost unbearable to her?
Overall, the one piece of advice I have is to have the autism as just a part of that character's life. It doesn't have to make her a burdensome "child in an adult's body", but it doesn't make her some kind of superhuman genius either. Talk to Autistic people about our experiences, because we're all different. A lot of us may have issues in common, like most of us struggle with a lot of anxiety and find the unwritten social rules of society a bit arbitrary and confusing, outside of that though, we can vary hugely.