Frenemies Lauren Conrad and Heidi Montag kiss and make up -- and "Extra" made it happen!

The "Hills" starlets ran into each other at STK, where "Extra" was with Conrad at the exclusive after-party for her fashion show -- when nemesis Heidi and beau Spencer Pratt suddenly showed up!

Speidi tells "Extra" they were unaware of Conrad's party and were just stopping in for a drink on their break from shooting "The Hills" down the street. When Montag saw Conrad arrive, "Extra" witnessed the former BFFs exchanging a polite "Hi" before Lauren went into her separate party room.

At the fashion bash, L.C. revealed to "Extra" that Heidi was "cool" -- and "it was no problem she was there" just as long as Spencer didn't cause any trouble. Heidi then pulled an "Extra" producer aside to say she wanted to chat with her old roommate -- and "Extra" brought them together!

The girls chatted for a moment -- then both suddenly burst into tears and HUGGED! After the tearful reunion, Heidi personally thanked "Extra" for arranging the impromptu meeting, and said of Lauren's clothing, "It's a great line and I love Lauren, so congratulations." Even Spencer expressed his support of Conrad, saying, "Congratulations, L.C."

Is this the beginning of a new chapter in the ongoing Heidi/Lauren saga? Only time will tell -- and only "Extra" brought the starlets back together again, at least for a night!