Wilma

There is a Lithuanian family who lives down the street that we sometimes fraternize with. It was great when Abby was little because they have 3 kids- An older girl named Monica, Wilma, who is in 1st grade, and Adonis who is Abby's age. We used to play in their yard and Abby would follow Wilma around (when Wilma would permit it) and they would play ring around the rosy and wear the Abster out when I was killing time before Tim got home.
This stopped last summer because I found that Wilma would get kind of rough with Abby and was not very nice to her. I like the mom enough, she complains about her husband constantly and talks about moving back to Eastern Europe. And Monica is a good kid, she just started junior high and isn't adjusing well. She is interested in things like iPods and boys, which her mother has forbidden. She thinks I hung the moon because sometimes I help her with her homework, and I let her come over and use our Internet. But Wilma is kind of a nightmare. She is the ultimate middle child and I think she would light her hair on fire for attention. I usually like those kids, but Wilma is just not very nice. We would come home from their house with Abby in tears more often than not so it stopped being worth the time.
Today I was passing by the elementary school in our neighborhood while all the kids were out at recess. I immediately saw Wilma (her white blonde hair is hard to miss). She was talking to a boy who pushed her down and kicked her before running away. Wilma got up and just stood there. I kind of paused for an extra minute at the stop sign to see what would happen next. She walked over to where some girls were playing and stood there, they seemed to be talking, but then all the girls ran away. Wilma stood there. I had to move, and I didn't see what happened next, but I felt bad for Wilma. I couldn't tell if she was being the Wilma I know from the neighborhood, of if the Wilma I know from the neighborhood was a product of what happens at school. I felt bad for her.
When we went for a walk this afternoon we passed Wilma's house. She was jumping rope, and came running up to us to see the baby. Abby tried to play with her, but Wilma pushed her. I was a little more forgiving of this than usual because of what I had seen earlier. I asked her how school was, and what her favorite thing to do at recess was. She told me that she hated recess because Monica wasn't there anymore to play with her. I felt so sorry for her. Monica's big move to junior high had been tough on both of them. I let her terrorize Abby for as long as I could stand it, and we continued walking. Abby doesn't notice that Wilma is not very nice to her. I guess that is a good thing.
One of my biggest fears is that I will have a kid who gets picked on, or worse yet, I will have a bully. I don't think that Abby is capable of being a bully because it doesn't seem to be in her nature. Her nature is so sweet (in my humble opinion) that I fear that she is going to be the victim of many mean girls in the future. How do I fix this?