I had to manage horses like this before. I’ve noticed that solo horses get excessively proprietary of their fence-line. Don’t know if it’s because they’re insecure, or what, but they talk big game around the fence-line because they know the other horse can’t put them in their place. It’s worth investigating ulcers here, and moving her to a bigger pasture with a buddy and no shared fence-lines (if possible). She sounds anxious and insecure.
Kicking out at a fence line is how horses get killed. It’s absolutely unacceptable behavior. She needs to be discouraged from doing this. Tie her up in a safe area so she can’t rile up the others and hurt them in the process. If she absolutely can’t be tied and must be fed free - growl at her, clap at her, throw a bucket, whatever needed to redirect her away from the fence. All it takes is one kick for you to have an emergency vet call on your hands. BTDT.
Bucking and general shenanigans is fine, as long as it is not next to a fence.
Short term management solutions include lining the stall (or kick area) with a stall matt - most of these horses kick out because of the spectacular noise it makes. You can also try feeding her first or pulling her out before grain.
She is putting other horses and your co-op barnmates at huge hazard with this behavior.