GF (18) had to reject her best friend, and is now devastated, what can I do?

My (18M) GF (18F) and me have been in a long distance relationship for ~2.5 years, with getting to meet each other every now and then (thx to summer break, I was able to go to her town for 1 week, last week). She has bin friends with the mentioned person (19M, I’ll refer to him as “N”) for a long time, since they went to the same school and had some courses together. Last year she moved, and the two were texting every now and then. N has a pretty tragic past with being abused and rejected and left behind basically all the time. My Gf only learned that about half a year ago, when he opened up to her. For a long time, she was his only friend. Since N had a lot of hardships within the last 6 months, he always turned to her tomake him feel better, give advice etc. Since N was very needy at times, that means she had a lot less time for me, even on more or less special occasions, like valentine’s day, which left me very jealous at N at times. To go against that she introduced me to him, and we texted each other too, every so often, and we got along pretty well, which helped me to be less jealous. However. I was not introduced to him as her Boyfriend, since she didn’t want to make him feel unneccessary. Since I don’t want to leak too much information about N, I won’t go into detail, but it makes sense, that he would feel that way in such a situation, trust me on that. A month after N and I texted for the first time (with me playing the role of just a very good friend of my Girlfriend’s), he suddenly decided to stop being in contact with my Girlfriend. They didn’t text for about a month. When he came back after some time had passed, he gave the reason for this to be, that he “wanted to give us time to focus on ourselves” since he somehow felt that me and her probably have romantic feelings for each other (despite not talking much about each other, when talking to him). So he came back, and they were friends again, just as before. Until I decided to visit her. N learned about this from her. The weekend before I went to visit her, he texted me, and her, telling us, that he would keep himself back from texting either of us, since he wanted us to “focus on ourselves”. On Friday I went back home, everything was fine. Then yesterday N confessed his love for her, as she was the only person who made him feel special, ever, but he also mentioned, that he knew telling her this was hopeless, since she seemed to have had romantic interest in me already (and she is not polyamorous). This lead to my Girlfriend obviously having to reject him, which devastated her, as she is very sensitive about emotionally hurting people, and losing her best friend, to a point where she now doesn’t want to have anything to do with anything, in order to not make things worse for anyone. She doesn’t really answer and doesn’t want to call me either (she usually did that when she felt down). She blames everything on herself. Right now she is devoid of all happiness and doesn’t want anything. Is there anything I can do for her, to help her move on?

Tl;dr: title + hard to reach out to her