The Insider.com

Talk about stealing your own sister's thunder!

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Rumer Willis attended Le Bal des Débutantes at the Hotel Crillon in Paris over the weekend, celebrating little sister Tallulah's entrance into high society.

But Rumer's attire seems less than appropriate for such a frou-frou event, as she sported a plunging silver v-neck dress that certainly gave everyone at the debutante ball an eyeful -- not to mention her Twitter followers when she obliviously tweeted this photo of her alongside Tallulah and Scout Willis Saturday night.

Wonder what Bruce Willis, who was also in Paris for the festivities, thought of the super revealing gown?

But what do you think? Is Rumer looking seriously sexy, or is her dress in poor taste for the event?