So my new pullets were putting themselves to bed every night and all was well. Then one night, none of them would go in the coop. I had to put them to bed. Turns out, the big girls had gone to roost first that night and the pullets, wouldn't go in. So I pulled the older layers out, and as I did this pullets marched right in and roosted.
Your problem, might be Alberta...if she is already in the coop when the little ones are ready to roost, they may just decide to sit outside.
You might have to pickup Alberta around bed time, and hold her till all the little ones have gone to bed, then let Alberta go to roost after the pullets.