You don't need to comfort her. Every time he complains to you, you listen to him quietly. When he's finished, complain as much as he says, making him feel comfortable. In fact, she really doesn't need comfort, and she probably doesn't need comfort. She just wants to find someone to complain to.

Just like me, when I first came to our dormitory, I felt that the dormitory was particularly poor, far worse than high school. At least, high schools have separate bathrooms. When I was in college, I didn't even have a separate bathroom. Besides, other people's college dormitories are all under the table. We just went to bed, and there was a big rotten table in the middle, and there was no stool. When we want to do our homework, we have to buy a small table to write on the bed. Sometimes I complain about our dormitory when chatting with others. I will tell him all the edges and corners of our dormitory, show him how bad our dormitory is, and show him how miserable I am. Maybe I just want him to feel the same way about me, so that he can feel my feelings.

But I don't want them to comfort me either. I just chatted with them casually. I didn't mean to comfort them. And usually when I tell them, they laugh at me and they don't want to comfort me, so your friends may not need comfort. He just wants to talk to someone. He just wants to pour out his thoughts and find someone to listen to.

Maybe his thoughts are similar to mine, so I can understand him better. When he complains to you again in the future, just ignore him and keep listening. He needs a listener, not a comforter.