Rumer Willis -- I'm Ready to Party Again

Rumer Willis returned to the Hollywood party scene last night ... slinking into a SAG Awards after-party just 6 days after her mother partied her way into the hospital last week.

Rumer -- who was at her mom's home when Demi went into a semi-conscious, convulsive state last Monday -- was seen entering the legendary Chateau Marmont hotel on the Sunset Strip last night ... by herself.

As we previously reported, Rumer and Demi had been partying together in Hollywood just 2 weeks before Demi's medical emergency.

We're told Demi is still receiving treatment for substance abuse.