The argument began when McCarthy tweeted (and deleted) late last night, "Police are at @AmandaBynes house. I hope they get her help. Enough of this circus. She needs help."
The VH1 host posted a barrage of tweets from a publicist named Jonathan Jaxson, who claimed that the NYPD was at Bynes' Manhattan apartment (though police sources tell E! News there's no truth to that).
The "She's the Man" star then lashed out, saying, "@JennyMcCarthy I need help? What are u talking about? Aren't u 50 years old? I'm 27, u look 80 compared to me! Why are you talking about me?"
And added, "@JennyMcCarthy you're ugly! Police weren't at my house old lady! Shut the f--k up!"
McCarthy offered an apology, saying: "Sorry girl. Looking out for ya."
The back-and-forth comes on the heels of Bynes posting several seductive topless photos of herself yesterday on Twitter.
Looks like she had one very busy Wednesday, but at least it ended in on a good note!