It could be any of the minor royal males. Earl Snowden (viscount linley back then) and Freddie Windsor were both known cocaine users.
Freddie Windsor basically said that they were all into it in the circles they moved in.
Peter Philips hasn’t been an angel. And there are umpteen windsors that could potentially fit the bill - especially as I doubt Rebel Wilson is able to recite the line of succession from the time spot on.
Given she named Baren-Cohen so openly I doubt she’d be being coy if it was a big name royal.