You need to intervene in the treat issue, even if it means no treats for awhile. Make sure that each dog gets it's treat, and the other doesn't steal it. You may even have to crate Abby and Chloe when the treats are given. You may also try smaller treats that can be readily eaten without having to break them up to chew them first.We also have two females, and one, Gunnr, is more dominant than the other, Tika. They are not allowed to take each others treats, end of story.
It's up to Abby and Chloe to determine their relative position on the social ladder, and other than an all out fight, you may just want let them work it out. Dogs understand who is above and below and don't harbor jealousy about it like a human would. For them it's normal, and it's actually healthier for them to establish their own position . Even though you are trying to treat Abby as #1. You will be better off in the long run ensuring that both are treated equally.
You are the "Top Dog", if you will, and both dogs have to understand and accept that on every level. In your social hierarchy it's healthier for both dogs to respect you as #1. If Chloe percieves your overt attention to Abby as submissive, she may interperet it as Abby being #1 and you being #2 and possibly try to place herself between you and Abby. In essence she will compete with you and not Abby.
In Sarahf's post, she used the word "humanize" to describe some behavioral observations. The word Anthromorphism would be the same as humanize, in that we attribute human emotion and response to non human creatures. Dogs don't "get even" with malice or forethought, but they will act out, and experience emotional behaviors. ( This is validated by university studies, though anyone with a dog could have told them that dogs do have emotional responses, without a goverment funded study.) Both Abby, and eventually Chloe, may begin to act out negatively to gain attention.
It will take time for everyone to understand their roles, but you'll get there.