The adventurer party better all be okay after she dies, it better be one of them "if the head vampire dies the turned go back" kinda rules! IK shes a zombie so what?! LET ME COPE DANGIT
At the moment, this seems like it's most likely the case based on what Silkie said and how Yui was having a conversation with the Zombie a few chapters ago. It also makes sense as part of the plot because it makes Yui a tragic character, an innocent child being manipulated to do horrible things. Also, if I remember correctly, despite being a serial killer Silkie doesn't want to kill innocent people so when you toss these two things together it would be interesting to see how killing her would effect Silkie.it does make me wonder if the virus is in charge of her... not the way around.
because she acts extacly like a virus would do.. attempting to spread itself around by biting, spitting and such.