Aggressive juvenile silkie?

[Chikenshiken]

I have a maybe 4 month old silkies who are just starting to grow their waddles and get bigger crowns. My bigger probably slightly older silkies has been bullying her sister nonstop today! And it’s hard biting on the neck that’s very concerning I usually just let chicks spar but this seems far beyond just regular sparing. I separate them for a bit and when they’re reunited the bigger chick goes right back to trying to fight her sister. They’ve been together since they were babies so I’m extremely confused where this sudden aggression is coming from! Any advice?

 

[sourland]

Any possibility the larger chick is a cockerel trying to breed the other?

 

[Chikenshiken]

Any possibility the larger chick is a cockerel trying to breed the other?

I’m pretty sure both of them are female and even if one was a cockerel I’m not sure it’s even at the age where it would be mounting other chickens. My chicks voice hasn’t even dropped properly yet it still chirps