According to Wikipedia, Diana appeared in three episodes of Perry Mason. The first is The Case of The Resolute Reformer. The second is The Case of The Unwelcome Bride, where she is the one on trial. The final one is The Case of The Bouncing Boomerang. Quite the title, huh? Diana is the victim in that one.
I think that the first one has her on the witness stand. Her alibi was that she was driving in an all night sports car rally. Which sounds like something that Diana might actually have said.