Garza -- who has 6 kids -- went after the "Zero Dark Thirty" star after she tweeted about a Senate vote this week that struck down an amendment requiring insurance companies to pay for contraceptives.
Chastain wrote, "#BirthControl is no longer covered by health insurance. Congrats USA, you're doing your part to keep women out of the work force. #smfh."
Garza no likey ... and responded, "It's called abstinence, a word that has been forgotten amongst this generation... it's the best contraceptive... #juatsayin."
So far, Chastain has yet to reply.