In the comics, Shriek debuted at the start of the Maximum Carnage event, where she was freed from the Ravencroft mental institution by the symbiote-powered serial killer and caused a lot of trouble with him and other unhinged super villains.
Since then, she’s bounced between continuing her partnership with Carnage and allying herself with other Marvel antagonists.
No specific details about Venom 2’s version of Shriek have been revealed yet, but if she’s anything like her comic book counterpart, we can presumably count on her working with Carnage as the story unfolds.