All three behaviors are normal. (Now that doesn't help at all, does it?) I think something a little different is probably going on with each cluster of children, so I would respond to each differently.
Stop the Bullying
The children who are falling apart right away when Sophie starts her teasing feel that they're being victimized-that Sophie is a scary bully. I never allow a child to bully others, so I would intervene calmly and immediately. I doubt that I would send Sophie to time out, though. Sitting on the sidelines isn't giving her any insight as to how the upset children feel. It doesn't give her the opportunity to see things from their perspective and a chance to develop empathy.
Instead, I'd say, "Tell Sophie that you don't like it when she's mean. Tell her in a big, loud voice. Tell her, 'Stop that right now!'" It's always important to help victims stand up for themselves and their rights-to dare to use their voice. "Walk away from Sophie. Tell her you can't play with her until she's nice."
If she won't quit, tell Sophie that you can see she's making these children sad and that making people sad isn't allowed in your classroom. Invite her to help you do something in the classroom, read a book on the rug, or play with another group of children. If you choose the latter, you may have to assist her in getting into the new group.
The children who sometimes enjoy the teasing, and at other times are terribly upset, may be pleased to be noticed and approached at times. At other times they may be busy and therefore feel intruded upon. When Sophie doesn't heed the behavioral cues they give and/or the words they say, they probably feel frustrated and helpless to "defend" themselves. You can help the children who are feeling bothered explain this to Sophie, and you can help Sophie find another fun activity.
Children sometimes experience teasing and being teased as fun. It's a form of human interaction. You have been noticed! Someone is reaching out to touch you socially! This is why some of your complainants are also, at times, the teasers. The best thing to do is to observe each child carefully. Respond to their behavior on an individual basis-depending upon what appears to be the problem at the moment. ECT