Well she may not do it (WON'T HAPPEN, etc...) but back in the day she did do a few scenes for Extreme Associates, when they were still churning out quality smut (...), which hinted at the possibility of her less-than-subdued performances....
Plus she also worked with Lexington Steele, who sometimes tries to push the (softer) girls into some "nastier" shit.
But I agree; Gwen had a certain som'tin som'tin which would make her fans "ache" with anticipation...