[expletive] star Monica Foster, who's accusing Lenny Dykstra of bouncing a $1,000 check to her for escort services, tells Breaking Celebrity News the baseball player-turned-businessman "is a coward" who "thinks he can just treat people like crap."

EXCLUSIVE DETAILS: [expletive] Actress Says Baseball Legend Lenny Dykstra Stiffed Her

We spoke exclusively with Foster about her run-in with with the ex-baseball great -- and the chain of events that unraveled.

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"He is a coward. I know in his eyes, he just screwed over a hooker and he thinks he can just treat people like crap because he was once a big name," said Foster, who's starred in X-rated titles such as Not The Cosbys XXX and Flava of Lust.

“I hope that by going public with this, his escort supply is cut off. I hope everyone can see that he is just worthless.”

Breaking Celebrity News’s repeated requests for comment to Dykstra's attorney, Moshe Mortner, have been declined. The baseball star "couldn't be reached for comment”, we were told.

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Foster told Breaking Celebrity News that Dykstra -- who carved out his baseball legacy as a speedy leadoff hitter for the New York Mets and Philadelphia Phillies -- "obviously has some money, because when I met him he was staying in a beautiful Beverly Hills hotel.