Rihanna Barely Holding it Together

8/20/2016 7:48 AM PDT

Rihanna -- Barely Holding it Together (PHOTO)

Rihanna was in a precarious position Friday night in London.

She knew how to do denim for sure, as she left Tape nightclub ... the same place Justin Bieber was partying with a mystery blonde.

28 Justin ... it's the new 17.