Well I would assume that Zombies may behave like the "traditional" ones of African folklore (for those who dont know that's where zombies come from lol). In that case they serve the basic commands given to them by their master(s) & will do that task until 1) They are told to stop, 2) Given a new task that contradicts the previous one or 3) The one controlling them dies (that 3rd option is more modern media than tradition).
If the Zombie is given the commands "Do Not Harm That Human" & "Open The Gate For That Human" than it shall do so. She is at least 300sh years old (Tinkerer said they were free for about 100 years before their 200 year imprsionment) & is the one most interested in the dark arts so makes sense she would have such power.
For example there is fridge logic here if you think about the Zombie Riderick fight. He wasent attacking MC, he was going for Oksana. But when MC began to attack him his most basic instincts (or what's left of them) had it attack him as well. So theoretically if MC attacked the zombie it may react violently against the command it was given. But for now MC is "cool" so to speak