Unfortunately the middle chicken even bullies her on the perch at night. Both the middle girl and alpha want the spot against the right wall. The alpha will peck the feet of the middle girl until she moves. Then the middle chicken will start to bully the baby until the baby decides to charge through her and go under her to get away from her. The order had to be the baby on the left, the alpha in the middle, and the aggressive middle child on the right.
Glad the little chicken was able to get some time at the feeder with a 2nd option being available.
Can you post photos of their roost set up and what they look like when roosted at night? Adding a second roost might be helpful in this case, even if there's only 3 birds.
What you're describing is completely normal though, even if you find it distressing. They're brutal to each other at roost time and will peck at one another trying to compete for the most desired spots.