"The Waltz," is Parker's most re-published story, but I doubt you will find an on-line copy free.  It is still under copyright and can't legally be put on-line. However, if you are close to a library, or have an on-line account with your library they may have a copy of her "Dorothy Parker's Complete Short Stories."  This contains a copy of "The Waltz."  You might also check in various short story anthologies as this story was republished in many high school English books.  Good luck, and for more information about this quaint story check out the links below.