I'll be the first to admit that I'm no animal behaviorist so I'm wondering if I can pick the minds of you all who have read into/studied animal behavior.
Pecking Order: Emma > Ella > Guinevere
Backstory info: Emma has the most confidence however Ella will test Emma time to time. Guin is a pushover for the most part. From what I heard when I got Guin, she was picked on by the other dogs she was with.
The behavior situation: If Emma is laying down, and Guin decides she's going to walk past to come get love or get on the couch, Emma gets grumpy, immediately gets up and goes after Guin's hind legs. I know how to stop/prevent this behavior. I would just like other's perspective as to why it happens though. If Ella did the same thing it's unlikely Emma would go at her. I assume this to be because Ella will not put up with it while Guin will do nothing about it. Emma did not do this before we got Ella. I'd also like to note, while it's an aggressive behavior, she's never "rough" with her just pushy and noticeably irritated, but I know it's not playing.
I've also noticed Emma has a bad case of FOMO (fear of missing out). If say, I'm going outside, and the other two dogs are allowed to go and she is not, she looses her doggy mind (whining, barking, trying to push her way to the other two dogs). I get that, but she's always worse when we do something and she's the last in line.
As I said, I know how to fix this issue, I'd just like to understand the behavior behind it better.