First, remember grand jury proceedings are nit trials. It's a one sided proceeding, in which the prosecutor presents evidence to the jury members seeking an indictment. There is no defense, no cross examination of witnesses, and the prosecutor only has to establish probable cause that tge offense occurred. The old lawyer joke that a decent prosecutor could indict a ham sandwich is true.
As for bias of a grand juror impacting the case, not sure how that appeal may turn out. On one hand, her statements demonstrate a clear bias, which should get her booted from tge proceedings. On the other hand, there is no right to appeal an indictment. Can't appeal unless or until there is an actual conviction after a real trial. An appellate court might just see that conviction as proof that, despite the biased grand juror, there was sufficient evidence to justify the indictment, or else there would have been no conviction.