There is indeed a lot of stress and not everyone deals with it well. Personally, my experience was generally positive throughout my graduate program even though my advisor was often away from the university and sort of left us to our own devices. Fortunaately the research group was large and I found a mentor in one of the postdocs and colleagues in the other students. The biggest stress was having to finish in a rush when my advisor died and trying to find a postdoc position without his help.
As a faculty advisor, I have learned over the years to be supportive of my students but also to give them the freedom to develop their research program themselves. I think that the key to avoiding the issue of solitude is to be in a research group where collaboration is encouraged. Of course, I can only speak for my own area which is physics and materials science. It is certainly true that other fields will tend to have a more solitary existence.
To the OP, your D should take these 2 years to figure out how she wants to balance her personal life and work and to decide if graduate school is really necessary for her ultimate goals. I have two sons, one decided early on that he wanted to pursue research and has taken a long but interesting path to his PhD and now a postdoc looking for an academic position. The other is an engineer whose professors were encouraging to think of graduate school. He realized that he was not willing to deal with the stress of taking more courses and decided to take a job after graduation. He has done very well, enjoys his work but does not let it dominate his life 24/7. A good choice for him.