Video volume too low when screen sharing on Blizz

I have a teacher using Blizz to share her laptop screen with my student with low vision, when she is screen sharing and tries to play a video the speakers connected to the laptop play at a volume that is significantly lower than when she's exited out of Blizz. We maxed out the volume on the speakers, laptop, and Blizz audio settings and still have this problem. It's not hardware based because as soon as she shuts down Blizz the volume goes right back up even within the same video. Any ideas what could be going on? Thanks.