It seems possible... Apparently Mary was pretty kinky in her private life. There is an interesting Rialto Report segment on Mary at the link below. It actually discusses this very scene (near the end, I think) as well as aspects of her private life...
Fantastic. Saw this on video back in the 80s. Always hoped to come across the scene again but didn't have a clue what film it was from or anything. Thanks for posting
https://www.therialtoreport.com/2019/03/10/mary-stuart/
Scene 8. Bree Anthony, Mary Stuart, Mel White