Introducing new pullet

[Thataussielady]

I have recently purchased a New Hampshire red pullet ( she is around 2 and 1/2 months) and have tried to introduce her to my flock.
The flock constists of:
1 laying d'uccle
1 point of lay pekin bantam
1 3 month old Wyandotte
1 3 month old silkie
AND 1 VERY aggressive Wyandotte bantam Rooster.
All of my usually sweet girls and rooster(who used to be quite tame) have now turned into little devils. When I first brought her home I decided to sit down but hold her to see what the flock did. Immediately my girls began to try and peck her to death but my rooster wasn't really phased which I thought was odd. I put her in a separate section of the coop where they could look but not touch. After quite a few days I decided ( since they didn't try pecking her anymore) to see what would happen if she was out. I made sure I could easily get to her and then let her go. She was fine just pecking on the ground with the other girls even if they did give her a bit of a nip. Of course nothing lasts forever and out of nowhere my rooster grabs her my the neck and starts to viciously mount her. It was just lucky that I was there or I'm sure he would have killed her.
Sorry this is so long but does anyone have any ideas on how I can try and introduce her?

 

[Happy Chooks]

First, when integrating, it's easiest if you have more than one. When you integrate one, they take all of the abuse until they are accepted. More than one, they can't focus on just one to chase and the abuse gets spread out. Chickens are flock animals and need time to adjust to new birds. A couple of days is not enough, it needs to be at least a week.

Now with that said, your flock is young enough that you should be able to get away with it. They are all roughly the same age, except the bantams, and they are small. The trouble is obviously your rooster. How old is he? He is trying to mate the young pullets and they aren't ready for mating. I would lock him up separately, and let the pullets (including your new one) adjust to each other. Then when they are older, and ready for mating, you can let him back out. If he is aggressive to people, then I'd advise finding a nice rooster. A mean one just isn't worth it.

 

[Thataussielady]

I do think now that I should have gotten more than one, but she was mainly a replacement for a hen we lost a few weeks ago.
I do get into the habit of called him a rooster but technically he's a cockerel ( 7 months old)
He is usually a sweetheart when it comes to people so I would really want to get rid of him.
I did take your advice and locked him away while letting the pullets together.
They did get along aside from the few pecks exchanged when they're was food involved.
The only trouble now Is my cockerel getting all fussy and starts crowing when his girls aren't right by his side. I doubt there's really anything you can do so he'll probably have to
Deal with it.
Thank you so much for your advice!

 

[Happy Chooks]

Give him a 5 days or so, then let him out and see how he does. Cockerels mature faster than pullets.