"I'm so over you."= I do not like or love you any more

it means that at one time I had feelings for you , but now those feelings are gone and now I am indifferent to those feelings.

"To be over someone" means you don't have romantic feelings for them anymore. You had feelings, but now you have got over them. Adding "so" gives emphasis, as in "so very much" or "so happy": "I am SO over you."

it means i don't have feelings about you anymore. And here is one reference:in"Friends",Rachel has told Ross she wanted to give the feelings for him up.So she told him"i'm over U" You can look it up in the series.