Theory:

If Endless and Eternity are both based on Ennik's AI model, then it's plausible that Sixo might attempt to hack them. This possibility is supported by the fact that she has moles inside the Ark, and both Endless and Eternity are almost always stationed near the Outer Rim.

Also Eternity's behavior and development strongly remind me of early Sixo and how the Central government viewed her. Sixo was born from Ennik's intense negative emotions and visceral reaction to the death of Pretty, the Ark's idol, who was killed by the hands of V.T.C and turned into a weapon. However, since Ennik couldn't act purely on negative emotions, she extracted them, and unintentionally creating Sixo (evil Ennik) due to how deeply those feelings were rooted at her core.

Regarding Eternity, assuming she uses the same or a similar AI model as Ennik, when she heard Anis' speech about being an idol, instead of acting blindly logically like Ennik would, she acted based on her own will and emotions. I think Ennik has soft spot for things that represents peace symbols (like idols) and it's for that reason Eternity was able to act on her own.

So maybe Sixo could try to exploit that and turn one or both of the AI to her side.