The answer lies within Alice, she is "technically" alive.
What I mean technically is, she is not dead yet she is infected by the T-Virus. Unlike zombies that are dead, and the flying moths that are composed and living AND relying with the T-virus to stay alive, Alice is human, a clone to be exact, but she has red blood cells, all the cells a human has. What actually happened to Alice is she became a normal human after resident Evil 6.
Do also take note that Albert Wesker removed the T-Virus inside her in Resident evil 4:Afterlife when Wesker is trying to escape and Alice surprises him from behind, he injects Alice with a serum that neutralizes the T-Virus inside her, making her human again.