This Is The Dancer Demi Allegedly Punched!

Demi Lovato's decision to enter rehab remains a bit of a mystery.

But now we have a little background info on the girl involved in the star's reported "physical altercation"!

According to TMZ, Demi actually punched Alex Welch, a Jonas Brothers Live backup dancer who appearend on America's Best Dance Crew: Season 3. And, apparently Alex, isn't too happy: TMZ claims has a "pretty nasty shiner" from the incident, and is considering legal action.