I think porn releases are generally along the line of "you surrender all rights forever".

It's possible someone paid an attorney by the hour and got a long document that itemized things. But most likely she's gambling this is porn, and nobody keeps silly pieces of paper for 15+ years, especially when companies fold, catalogs are sold, etc. She'll claim she never signed a general release and see if anyone can prove otherwise.

She was a pretty minor performer in few scenes; she's not even Lubben material. As said above Excalibur probably sold one title with her every year or two, usually from a customer typo; Heidi isn't worth the trouble.