Ford has contributed to Democratic candidates, though not a large amount, and her parent's appeared before Kavanaugh's mother, who is also a judge(in the mid-1990's). Either or both of these things could make Ford biased.
It doesn't mean that any of these people are biased, or that any are lying, but it does lower the value of their direct statements.
Yes, it lowers the value of her direct statement about being sexually assaulted by a very small amount, to an extent not even worth bothering with if not grasping at straws.