Revenge for the death of their leader.
As such, even though Aubrey was initially against using her blood for warfare, seeing the gruesome deaths of the kind who had fought so hard for her freedom, she eventually conceded. The goal was not to weaponize her blood but to make a synthetic version that could be used to strengthen the werewolves when ingested. After all, it would be impossible for her to always be present to assist in the field during a "confrontation." There was also the fact that her scent had the same impact on both species. So, it was imperative that a serum be created which could only be utilized by werewolves and on the condition that it would not be used for evil.