I mean, imagine it... Blackarachnia falling out of the sky onto the Ark, the Autobots finding her and reacting with shock to her organic half, her awakening and attempt to escape, only to be stopped by.. Optimus?
An older, taller, and much stronger Optimus.
(bonus points if she thinks this Optimus is kinda hot. But just a little bit. It's the voice, really).
So an indignant Blackarachnia has to stay and cooperate with these weird Autobots so she can get home. Needless to say, she hates it.
(double bonus points if she meets G1 Elita AND finds out about Prime's relationship to her) (and triple bonus points if Waspinator shows up, maybe with the Decepticons)