Rumer Willis At Demi's House During 911 Emergency

1/27/2012 1:28 PM PST

Rumer Willis At Demi Moore'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.