Demi, who is getting treatment for her "emotional and physical issues", allegedly assaulted 21-year-old dancer Alex Welch on a plane, after Alex told Demi's managers she had been acting out during her recent tour with the Jonas Brothers,.
"To this day, I haven't gotten an apology," said Alex. "I've heard nothing. That's sad if you think that person is your friend.
"We were on the plane with the Jonases having this awesome time and I didn't get a call or text from Demi or a, 'Hey, you got a problem with me,' nothing. And she walks up and punches me and literally walked away and got in her seat.
"No one should walk up and do that and brush it over, it's not right."
Her lawyer added: "We have contacted the Lovato camp and we are waiting for a response. If we don't hear back, we will pursue litigation."