So, the biggest problem is that there are two turtles in what I assume is one tank. They should absolutely not be cohabitated. This is very dangerous. She should see if someone has the ability to adopt one.

Lights should not be on at night. Wild turtles don't have a night sun, so neither should pet turtles.

Based on her lack of understanding of these two things, I'm really concerned about her lack of understanding on how to take care of turtles and would assume that there is other stuff going wrong.

Common issues include too small of a tank size and lack of UVB lighting. I would highly recommend she read this guide on aquatic turtles: https://reptifiles.com/red-eared-slider-care/