Difference between "lie on me" vs "lie about me"

I've heard people say both but I don't understand what the difference is, or if one is incorrect. I had always used the latter but I'm not sure anymore. Thank you.

Edit: thank you all for your responses. My apologies for not providing context earlier. Basically, I was talking to a woman - who happens to be African American - and she kept saying a woman from her job lied on her, meaning she was saying stuff untrue stuff about her. Thanks again.