At Demi's House
During 911 Emergency
Rumer Willis was at her mom's home when Demi Moore went into a semi-conscious, convulsive state.
If you listen to the 911 tape -- around the 00:54 mark -- you'll hear the caller ask, "What is the address Ru?"
What's interesting ... Demi was clearly smoking something and, we're told, inhaling nitrous oxide with her daughter right there.
Rumer, who is 23, was partying with Demi just 2 weeks ago in Hollywood.