It's real! It was shown on an official fan site of her, and if I remember it right, this picture was signed as published in US Plyby – long times before she was starring in TV-show "Sabrina - the TeenWitch".
She never has shown her beaver, because if you read the reviews of all movies she starred nude, she was only showing her tits, nothing more. Ok, in 1985 she played the leading role (billed as "Norris O'Neal") in the hardcore production "Bordello... House of the Rising Sun". In this plot she played a woman who inherits a whore house, but all her appearences were non-sex parts without any nudity. In the 80s she appeared in a second X-rated movie and some R-rated sex comedies, but always in the same way: no sex - no nuditity.
I think it's the typical part in a celebs young life, you can describe with: "I was young and I was needing the money!"
So I'm really sorry for you, there's no existing photo of her beaver.
Here's Beth up close and personal. From "Breast Men", 1997.
Download is AVI, 624X480, 2.85MB, 0:27