Room with glass windows as a walls.

Lots of glass windows? Is this a loft apartment with high reflective ceilings, hard uncovered or untreated floors. Very little furniture to dampen reflective sound waves?

Large open dimensional space? Starting with the windows is most likely the real killer in the picture, but also, just a beginning. To properly condition a space like this (assuming I'm correct) is a nightmare for an amateur. Hiring an acoustical specialist would most likely present a cost beyond the value of the system.

Sounds like you'll be chasing this problem around without much true acoustical satisfaction, For a long time.

If your daughter is a "serious listener" as opposed to just a casual listener, the sublime answer may be a good quality pair of headphones. Less hassle and less expense in the long run.

Admittedly however, the drapery treatment, as several have mentioned, plus a lot of cushiony furniture will definitely help the situation, without going crazy. Listening at lower volumes will help as well. But don't rule out component placement. Especially the location and positioning of the primary satellite speakers. I'm certain that some experimentation is this area will yield a number of different results.

I don't know what caliber of equipment she has. If it's just "mid-fi" as I call it, trying to treat the listening space is probably not worth it. 

If sound really matters to her, the other consideration might be to move at an opportune time. Then choose you apartment listening space carefully as much as other living space considerations.

@axpert  No, it’s not a loft apartment with a huge open space, and no reflective ceiling, floors are laminate. It’s one bedroom apartment with office room and living room divided by structural wall, but that wall is actually not a full wall and not connected with a glass window wall on the side, the space between them is approximately one feet. The system and speakers are facing this structural wall and the other window glass wall is behind the speakers. 

I suggest heavy curtains, a dense rug and DSP! I place acoustic panels along my windowed wall while listening. Gotta work with you have!

Many years ago the acoustics company I worked for was the 4th company to try to put in a sound system in the newly built Crystal Cathedral in So. California. Clearly it was an impossible job and our Lead engineer said they would have to put in satellite speakers behind every seat. Well that was to expensive but ultimately concessions had to be made to the look of the interior to get the RT60 to something  close to intelligible. Sometimes you just can’t win?

Obviously, the easiest audiophile solution would be to move and build a new home with a dedicated listening room and its own electrical source. Other than that, I can be of no assistance. Or... just enjoy life and the accompanying soundtrack to its fullest extent.