Leonie Granger from Gillingham, Kent, was sentenced at the Old Bailey having been found guilty of manslaughter.
Her boyfriend Kyrron Jackson, 28, and his friend Nicholas Chandler, 29, were found guilty of murder and jailed for life with a minimum term of 36 years.
Granger targeted Mehmet Hassan, 56, in a Mayfair casino in March last year.
Judge William Kennedy described the attack as "pitiless and wicked", adding: "It was quite simply an act of brutality which defies reason and compassion."
Granger's lawyer Orlando Pownall said she only took part in the plot as she was in love with Jackson and "fell in with his desires" and now "deeply regretted" her actions.
"Her head was turned by Jackson, who she loved, and to some extent by Chandler who was persuasive and superficially charming," he said.
But Judge Kennedy said she had been "deceitful from the outset" and had "lost her sense and compassion" when she got involved.
He added that she clearly cared more for Jackson than he cared for her.
Granger, who posed under the name of Rachel, was wined and dined by the divorced father of three who boasted to friends he was not paying her to be with him, the court heard earlier.
On the night he was killed, Mr Hassan had taken Granger to the upmarket Nobu restaurant before giving her Â£1,000 to gamble with at the nearby Palm Beach Casino.
The two were seen kissing passionately by a poker supervisor, before leaving the casino together for Mr Hassan's flat in Islington.
Granger then let Jackson and Chandler into the poker player's flat before leaving in a taxi.
Both men tied up Mr Hassan with parcel tape and a neck tie before kicking and stamping him to death, the trial was told.
Afterwards, while he lay dead in a pool of blood, all three were filmed on Granger's mobile phone throwing Â£50 notes around a room and even stuffing  them in their underpants.
Commenting on the footage, Judge Kennedy told the three defendants: "The eloquence with which it speaks about you is deafening."
A woman who set a "honey trap" for a professional gambler who was kicked to death for his winnings has been jailed for 16 years.