Hey Dev! It's amazing that you continued with this game! What they mean with "the blood of the female parasite" is you have to choose the female parasite from the ones you extracted from the mutants, not that the infected with the poison has to be a female. In the end you made the poison (at 27:52) and chose by pure luck the female parasite, which in the end killed the Mother. In fact, there is an "information" tab in the parasites area, which you selected briefly but didn't read (at 27:55). In this information you can read "How to determine the female of a parasite?" so you have to have collected all the parasites from the mutated animals in order to be sure you have the female parasite. You were lucky to both have the female parasite and choose the correct female one. So, yeah, it's necessary to have 4 parasites to ensure you have the female. With this information you can save Sarah too. P.D.: You did read the PDA information the last time, the one with the poison making information that you read here at 27:13.
