I seriously need some suggestions

I have three Orpington hens. Lily is the boss and 1 year older than the other 2 hens. She has a tendency to be aggressive but I am so attached to all 3 of them that I usually only scold her strongly when she gets ugly. And in the summer I have resorted to a water gun.
I have a timid buff hen Lilac who is half again as big as Lily. Usually I have only seen Lily being unreasonable when she (Lily) was broody. About 3 or 4 days ago I became aware that Lilac was being mistreated. She would scream when Lily even started in her direction, which was frequently. She is becoming more easily startled and will even scream if I startle her. I have not noticed any missing feathers or wounds. But she puffs up real big which I am sure to protect herself. I don't think Lily is broody, although she is in the nest box...a lot. In the past when she was broody she would not leave the nest. I am not sure if she is even laying. Lily is 2 yrs and the other two are 1 year old. I don't have the cage or the extra money to buy one to isolate Lily. I do have a peck and play which is a big mesh playpen type of thing that I used for the other 2 until I let them free range. I am not sure it could contain a full grown hateful hen. Plus there would be the issue of no nest box, but I have to do something to stop this behavior. I am enclosing a picture that I took this afternoon but it shows the much smaller Lily getting close to the much larger Lilac. She is puffed up like a marshmallow, in fear not in anger. What can I do? I adore all 3, but I am already dreading letting them out because of the way she is acting. Can anyone give me some advice (not to get rid of Lily)

If there are no missing feathers or wounds I would leave them alone and let them work it out. 'Pecking order' isn't something that is set in stone so it can be ongoing behavior. It could be that your older hen is a jerk, but just as likely that your younger hen is a jerk and the older hen is trying to put her in her place. Monitor it - if you notice injuries - then do something, until then, I'd let them work out their issues on their own.

Your hen is broody, that's why she's screeching and puffing up. There's no abuse or anything abnormal. Either break her or let her continue, she will remain broody for 1-2 months without any intervention.

It's not fear. That looks like the classic broody hen, 'don't mess with me' posture. Is she hissing and growling, too?

The one that is puffed up is the one being intimated by the smaller hen. I do not see any aggressive a action from her, rather the other way around. She bows right to the ground. Could it be they are both broody?

Do you know what? I believe you are right. Because I just went to get them out of the chicken coop and everybody came out except her. She is in the nest box and screams every time I try to pick her up. One to two months of this and I will be insane. I'm going to have to read online to find out another way to break this Behavior

Put her in an elevated wire dog crate. Use hardware cloth on the bottom, so it's more comfortable for her feet. And raise it up on 2x4s or cinderblocks. Don't put in any bedding, but make sure she's got plenty of food and water.

Now this afternoon both of the other 2 chickens started attacking her. I don't understand what has happened. They all got along well together until 2 days ago. I thought she was broody but maybe she is sick(?) I took the nesting material out of the nest box and she went back in there and laid on the bare floor. Others will attack if they sense a weakness. Being sick makes a chicken vulnerable but does being broody? I retired a year ago and I don't have extra money to buy a cage. There should be a way to stop a hen from being broody.....no?

She's not sick just broody, it's normal for the hens to fight with another hen when she's broody, it's just something they do. Chicken wire is cheap, make her a pen with it, elevate it off the ground by a few inches or put her on concrete. Ignore the drama, it's mostly noise.

How long do you think it will take before she quits being broody? And how can I tell that she isn't?