OP, my heart went out to you when I read your first post. Then I read your update and was happy for you.
I'm going to share my story anyway, hope you don't mind. When my DD started college her best friend from high school was supposed to be her roommate. The friend, at the very last minute, decided NOT to go to college so DD did not have a roommate when she started. Her two suitemates had boyfriends on campus so they left the room to go spend time with them, so my DD was completely alone.
We both cried when we took her to her dorm and had to leave. We've always been very close, so it was hard on both of us. Her major was journalism and she became a writer for the school newspaper so that helped, but at Christmas she ended up moving back home (even though she had gotten a roommate by then) and commuting (about a 30-minute drive). She had a few friends in college, but none she was close to. She had a part-time job here at home so that kept her busy on weekends, and homework kept her busy too. Fast forward a couple of years and she ended up dropping out of college and got a job at a local newspaper office, ended up leaving there a few months later for an office job at Wal-mart and this was back in 2000 so she has moved up the ladder there and is now the personnel manager and insurance tech. Married since 2000 to a sergeant at our local prison (he's working on his next promotion) and they have a 12-year old son and 8 year old daughter. They live a quarter mile down the road from us.
I understand your "empty nest" syndrome, as we, too, were empty nesters when our daughter went to college. So hard to get used to her not being here, but then it was nice when she decided to move back home and commute. Loved having her back! Then we lost her again when she got married, ha ha!
It's all part of life though, and you get used to it - then someday maybe have grandchildren to spoil.