Legal Question in Civil Litigation in California

Yes.

Sure she can sue, but if the agreement was properly drafted and explained the risks that pregnancy could still occur, she is very likely to lose the suit. The human body is incredibly good at re-vascularizing itself. For a heart bypass they pull a major vein out of the inside of the leg that runs from crotch to ankle for the bypass pieces, and the body just grows a new one. The same thing is far less common, but does happen, with both male and female reproductive tubes. Unless the doctor and the agreement failed to explain those risks, OR the doctor completely botched the procedure AND that can be proved after all these years, there is almost no chance she will win.