M.P.
This sounds pretty normal. The girls are learning how to relate with each other. Do not try to talk your daughter out of feeling excluded. She has to feel the consequences so that she will learn that the way she acts is a part of the problem.
I suggest talking with the mothers of Ally and Addy about what is going on. Are they also observing this? If not they don't know that their own daughters' behavior is not acceptable. Include a description of your daughter's inappropriateness along with their daughters'. Each mother has the responsibility to teach their daughter appropriate social behavior without making judgments. These girls don't know the appropriate behavior. They need guidelines from adults as well as the opportunity to feel first hand the results of the behavior whether it's appropriate or inappropriate.
I also suggest that you arrange play dates with other children so that your daughter can learn about having a relationship with a child on whom she isn't so dependent. I suggest that she focuses on one girl because she feels insecure and she admires something about these girls. She doesn't know how to relate to other girls. By providing varied play dates you're giving her the opportunity to have success in relationships which will increase her own confidence.
Perhaps you could enroll her in a dance class or tumbling or now that it's summer a swimming class. Success in new experiences can also increase her self-confidence.
My granddaughter recently turned 10 and has had similar experiences since first grade. Girls frequently pair up and exclude other girls. I see my role as grandma to help my granddaughter sort out her feelings in a way that not only allows her to see how she contributes to the situation but to also understand the dynamics. I ask questions and try very hard to not give answers. Over time I've found that the groups pair up, split up, pair up in a different ways, split up, on and on. No pair is a pair for very long.
I think I've helped my granddaughter to realize that the less attention she pays to anyone who is ignoring her the more likely that person is to coming back around to being her friend. Same for someone who picks on her. Ignore that person and she gets bored and moves on to someone who will respond.
It's so easy to get our own past experiences and pains mixed up with our daughter's and granddaughter's. Try looking at your daughter's situation only as your daughter's situation without connecting it to your own childhood experiences. Yes, on the surface they are similar but your daughter and these girls are different then you and the girls from your past. What remains the same is that these girls are learning how to get along and need your assistance.
My granddaughter goes to the same school as her mother attended. When my daughter, her mother, attended the school had a group for girls called a Friendship Group moderated by the school counselor. When my granddaughter began having difficulties I told the current school counselor about my daughter's group and she began a similar group in the present. It had helped my daughter and has helped my granddaughter and other girls learn much. The group consists of various aged girls and they share experiences and ideas and the counselor adds to them. I think one of the best parts of the group is that the girls are able to talk freely about how they feel and are able to search amongst themselves for possible solutions.
As an adult, when I've been with girls who taunted another girl, I told them that they were being mean and were to stop. I did this when my granddaughter was both doing the taunting and when she was the one being taunted. Kids learn how to behave from all of the adults in their lives. It is our responsibility to intervene when kids are acting inappropriately. I word what I say in a nonjudgmental way, usually expressing how I think the girls are feeling and the effect of what they say or do.
I've been a Girl Scout leader's helper, a playground volunteer, a YMCA volunteer an adult chaperone, and sometimes just another adult standing in a group.