I FOUND A SOLUTION!!

I know you were all trying to help but there is seriously something wrong with the way the tenant menu displays friends. This is my friend, we're on each other's friendlist, and I suspect there is something wrong with the system! I tried refreshing the tenant list by changing "oldest" and "newest" and I noticed NOTHING CHANGED.

Here is how I finally worked around it: from my friendlist I selected my friend's name and chose "assign friend group" and chose whichever. On the tenant menu, I used the filter to show only friends in that group instead of "all friends" and voila! My friend's name was finally there for me to choose!

It was rather frustrating since my friend was perfectly qualified to be a tenant but I hope this helps anyone else who might come across this problem.