Kayla would not be able to watch a YouTube video on oral sex instructions without confirming that she was over 18 years old first.
During the screen footage montage at around 17 minutes, there's a clip of the music video for Girls' Generation's "Holiday", released in August 2017. Later on in the film, at around 44 minutes, there is a calendar in Kayla's room that shows the current month as June 2017. Unless Kayla didn't change her calendar for 2 months, it's impossible for her to have been watching that music video.
In the mall scene where Kayla first walks in to meet Olivia, she walks past a number of mid-mall kiosks. One of them has a mirror and you can see the crew briefly reflected as she moves through the scene.