Like a Soap Opera
The elements of suspense are there in the opening lines, but there's very little showing (and more telling) in the writing style. Lots of explaining the situation rather than us witnessing it firsthand. We are told about an experiment that occurred, though we never know specifically what happened in that experiment that caused the zombie outbreak. I would've liked to have seen a more emotional tug in the MC's heart. She seems overdramatized and unreal. Why is what she did so terrible? The mystery aspect of this can be performed in a way that isn't confusing to the reader.
Read the story now
The relationship between her and her sister and the terrible things that happen as the story unfolds don't feel emotional at all. In fact, they almost seemed humorous. What with the "No! Audrey!" and the final "I love you," and the lack of internal thoughts while all this happens, it feels very soap opera-like.
I would suggest adding more descriptive language, more internal dialogues, maybe a flashback or two depicting the inner turmoil Anna experiences during the experiment, how she was involved, etc. As it is right now, I feel confused and disconnected after finishing reading. I want to feel more of Anna's strife, be more connected. I want to see the zombie's grotesque-ness. I want to breathe in that musty old room. Hear the crackling of the reporters voice on the news. I want to be there (metaphorically, lol)