What's your source?
If you have a quote from Mrs. Alito saying that was why she was crying, that would put the claim that she was crying over Kopechne to bed.
It's generally assumed that she was crying over the Democrats' treatment of her husband. I don't know of any other reason she would be. But if you really want a quote, I remember Orrin Hatch saying that was the case. It was on Drudge just after the incident.