The Forbes sentence naming Lady Gaga sits in its Hotel Imperial section, oe24 documented her 2010 arrival there, and Ritz-Carlton says its Vienna hotel opened in 2012; this disproves the specific sourced Ritz stay assignment, not every possible later relationship.
A Lady Gaga stay attribution attached to The Ritz-Carlton Vienna is based on a mistaken reading of the cited Vienna sources. The Forbes guide used for the attribution does discuss The Ritz-Carlton, but its sentence naming Gaga as a hotel guest appears later in the separate Hotel Imperial section. Contemporary reporting from Gaga's November 2010 visit also identifies Hotel Imperial, while The Ritz-Carlton Hotel Company says its Vienna property did not open until August 2012.