Lady Gaga Lawsuit -- Whiney Former Assistant Claims GaGa Demanded Towel After Shower

In what reads like one of the biggest sour grapes lawsuits of the year, Lady Gaga's former assistant claims she was a slave to the singer, having to do such unconscionable things as fetching a towel for her after she showered, and keeping GG on schedule!

Jennifer O'Neill says in her lawsuit ... she worked for Gaga for 13 months, and is owed $380,000 in overtime. O'Neill says in her suit her job included "ensuring the promptness of a towel following a shower and serving as a personal alarm clock to keep [Gaga] on schedule."

O'Neill claims she had to cater to Gaga in "stadiums, private jets, fine hotel suites, yachts, ferries, trains and tour buses."

And, O'Neill says, she was required to be at Gaga's beck and call at her "earliest waking hour."

O'Neill is suing for the $380k -- which represents 7,168 hours of overtime during the 13 months.

Gaga is not a defendant. O'Neill is suing Mermaid Touring Company, which Gaga uses for concerts and what not.

Gaga's rep told the New York Post the suit is "completely without merit."