Why are they picking on hennie??

[aart]

My outside run is 20x20 and the coop is 15x20, I am going to try and let her in the big run with two of the sweet hens and see how that goes....i let her out in the big run by herself yesterday and she was scared at first but got settled once she knew none of the others were in there...

Sounds excellent for 6 birds, assuming those are feet measurements.
What is your climate/location?
Does your run have lots of 'diversions' and 'hiding' places?
Places for the new birds to hide 'out of line of sight'(but not a dead end trap) and/or up and away from any bully birds. Roosts, pallets or boards leaned up against walls or up on concrete blocks, old chairs tables, branches, logs, stumps out in the run can really help. Lots of diversion and places to 'hide' instead of bare wide open run.
Multiple feed and water stations would help too.

 

[sbhkma]

Have you given Hennie a thorough exam? Checked under her wings and around the vent for mites/lice? Felt her breast to see if it's thin? Check her belly to see if it's swollen? Smell her breath and feel her crop-breath smell sour or rotten? Crop feel hard, empty, full, squishy? Have your birds ever been dewormed? Most likely something's going on with her and the other flock members know it. All the things aart pointed out are excellent tips for flock management. But you need to address whatever is going on with Hennie as well. It may be as simple as she's molting and very uncomfortable which the others are reading as a weakened condition. It may be more serious. But pretty sure there's something going on.

 

[tamsteve143]

She is molting, all of them except one has molted. The top hen is molting bad too, maybe she is just moody, not feeling well. She jumped on hennie as if she was a rooster last weekend and that's when hennie got petrified.