So far, I have not thought about it - for adding to the harem, I would like the character to be at least minimally developed.
Considering that the infected require a lot of damage to be killed for sure - she may return, but it will be much later.
I have it in mind. Not much to speak of right now - just a plan to make a several routes, when MC can be more on a human side, rejecting symbiotic girls, neutral (trying to come to the coexistence of humans and symbiotes in the end) and take a side of the symbiotes and help them to devour the world.