What does "you're on to me" mean?
"Be on to someone" is an idiom that refers to discovering and knowing the truth about someone and what they are doing. Usually, "be on to someone" refers to knowing about someone's behaviors that they have tried to hide because they are suspicious or unfavorable. Ex: I was on to my coworker when I saw him stealing money from the cash register. Ex: She was on to her friends when she overheard them talking about her.