You are allowed to make new friends, even as an adult. As someone who has lived in a dozen cities in my adult life, it does take effort. But it seems like, as the author is willing to take the effort to track and adjust their life, they are likely willing to put in time to make new friends.

I've found meetup.com to be an excellent way to make friends, as well as hobbies. (for me, standup comedy and DJing were excellent).