Can't Follow one of my Friends.
I can see my friend's account by going to duolingo.com/thiername but the green "Follow" button does not appear.
Wait! It didn't work. If she goes to her settings it looks the same as mine except she is missing Profile, Duolingo Plus, and Privacy options on the side
Can she get to settings? After you get to settings ... look for privacy (mine is at the bottom) ... She might have to hover/click/tap her profile picture to access settings.
EDIT: If she is on the app, try going to desktop mode or through the web browser at duolingo.com