This looks like a hen to me. Are you sure your leghorn isn’t trying to mate her? Or maybe they are going through the pecking order? Easter eggers (I think he or she is one) can be kind of soft, so they can be bullied easily. I’m pretty stumped on this, but I think that separating her (or him) is a good idea for now. (But, you can’t just keep her/him out of the pecking order forever. Then I think he/she will never really get into the flock. If you can confirm it is pecking order, you should try to let them figure it out, but be sure to keep an eye on her.) (but for now keep her separated)