being "all over" someone usually means that you like them a lot and/or that you are being clingy with them. "She is all over her boyfriend tonight" means "she is hanging on/cuddling with/kissing her boyfriend tonight" "I'm all over this band!" means "I really like this band!" In reference to a couple that has broken up, being over them means that you no longer care about them and the break up isn't bothering you anymore. "He's completely over his ex-girlfriend." "He doesn't care about her anymore." "I am so over you." means "I don't care about you anymore" I think it's very rare that someone would say "I'm all over you" in reference to a break up, but it's possible in certain contexts.

I think Ellen has nailed this one. I think she's hit it out of the park. You like colloquial speech...right, Nozturk? Okay, enough jokes. Ellen did a bang-up (oops, sorry) fine job on this. In her last sentence, she mentions "I'm all over you". This sentence doesn't make sense in a slang fashion nor does it makes sense in a literal or more formal fashion. You can say, "I'm over you" which means I don't care about you anymore.

It would be best to get the context of this sentence. "I'm over you" always means "I am completely done with you." I'm all over you probably means the same thing depending on the context.