Katrina Bookman took a selfie showing the machine saying “printing cash ticket $42,949,672.76” at the Resorts World Casino in New York last August.
But she was escorted out and was told the next day she could have just $2.25.
Her lawyer said he had tried for months to get the casino to offer more money.
The lawsuit filed at the Queens County Supreme Court said the Sphinx slot machine’s “bells, noises and lights” as well as the message on the screen told Ms Bookman she had won the jackpot, Courthouse News reported.
The subsequent disappointment left Ms Bookman anxious and depressed, the report said.
She is seeking damages from the casino for failing to maintain the slot machine as well as two companies that make and operate games machine, reports said.
A Resorts World spokesman said at the time that the machine had suffered an “obvious malfunction”.
The New York State Gaming Commission said the machine had been displaying a disclaimer that said “malfunctions void all pays and plays”.
But lawyer Alan Ripka told US media at the time that the casino had not responded to requests for an explanation about how the slot machine malfunctioned.
Before filing the lawsuit, Mr Ripka had reportedly been asking the casino to provide the Sphinx slot machine’s stated maximum payout of $6,500.
In 2011 the Iowa Supreme Court denied an 87-year old grandmother a payout of $42m after a Miss Kitty slot machine showed a message saying she had won a bonus of that amount.
The casino said it had been a malfunction and offered her $1.85 based on the symbols the machine was displaying at the time.