She eats, that's for sure, she's a big pig actually lol but the rest of the time is definitely spent sucking. She only used to do it a few times a day but now she can't leave the fences alone!
Cribbing/windsucking is due to stress, especially gastro intestinal stress/pain from inappropriate feeding, lack of free movement, etc. If it's allowed to become a habit, it becomes an 'obsessive compulsive' disorder and is very difficult/impossible to stop the horse, as it's self reinforcing. If the horse has got noticeably worse lately, I'd be looking for the cause. Stomach ulcer, hind gut acidosis, for eg.
Getting/keeping the horse healthy, in a healthy environment where it can graze, interact with others, free movement, will help by treating/removing the cause, but many horses are firmly 'addicted' and removing posts & such, running an electric wire around the top of fences, etc, &/or a cribbing collar is about the only option if you need it to stop.
I don't believe horses copy this behaviour. There doesn't seem to be any evidence of this. Horses kept in the same management may end up with the same problems though.
Eating/chewing wood can be a different beast though. May be simply there are nutrients in the wood that are lacking in the diet, may be the wood just tastes good.