If she's not doing well where she is I suggest moving her. Nothing bad with come out of moving her to a better place
NOW! Better to be safe that sorry
Now is time! Move her before she's seriously injured.
You'd be best to take her out of the current paddock she's in, or change her paddock mates. I think now enough is enough. Especially because she's becoming lame
I would say it is time to say enough soon. You don't want to risk a huge setback from lameness
I would definitely talk to the stable manager or who ever's in charge and request a change of pasture buddies. It definitely seems more than just establishing pecking order as it has gone on for a long time and seems that your horse is in danger of getting injured. Hope things improve for you and your mare!