Kelly Osbourne tells Paris Hilton to "grow up" after the two ran into each other at Coachella.

Us Weekly exclusively tells how Osbourne sent out a message on Twitter to Hilton saying, "Please grow up there is no need to act like a child," and added "You could of happily joined us! it's not 2005 no one cares!"

According to a source, the incident between Osbourne and Hilton occurred during the Neon Carnival. Osbourne was invited to join a table and after taking a seat Hilton, along with her sister Nicky and Brandon Davis arrived at the event. As soon as they arrived the group asked if they could sit at the table Osbourne was at and the event organizers than asked Osbourne to move to another table upstairs. Osbourne agreed to do so without asking why she had to move.

Osbourne and Hilton have been friends with each other for quite awhile and the presumed feud between the two of them dates back to 2005. Back then. Hilton's then boyfriend Stavros Niarchos, supposedly wrecked Osbourne's 21st birthday party. However, since then both have moved on the the incident.

However, Page Six reports that Hilton doesn't understand why Osbourne is upset. Hilton tweeted:

Photo courtesy of Kelly Osbourne's Twitter page

Photo courtesy of Paris Hilton's Twitter page