Glass walls are rough. If there's ANY possible way for her to hang acoustic clouds on the ceiling, that would be my suggestion. You can make them yourself for super cheap or order them from a company like GiK Acoustics. Minimal issue, just need to cover the holes and paint that part of the ceiling when she moves if she's renting. Also not sure if every single wall in the room is glass, but if you can get paneling up on any of the NON glass windows, that would be ideal.
And one more suggestion would be, if she can stomach it, use adhesive or command strips and hang at least a decent size section at first reflection 4-6" thick of the thicker stuff on the window where her first reflection point is. Or again, buy some panels from GiK for first reflections. With clouds, and first reflections covered, and if her rear wall is not glass, putting some diffusion on there, would help massively! Best of luck to you and to her!