Nick Cassavetes' Baby Mama Says Nick Needs to 'Get a Grip'

Nick Cassavetes' baby mama Heather Wahlquist says she wants 100% custody of their 13-year-old daughter until Nick cleans up his act.

Heather appeared on "TMZ Live" Wednesday and chronicled what she says is a custody war that erupted without warning. She says she left Nick in 2012 and everything was square between her and the director of "The Notebook," until this month when Nick went after her for not turning over Barbie for the holidays.

TMZ broke the story ... Heather signed an agreement promising to turn Barbie over on December 18, but she didn't and claims it's because she questions Nick's stability, insinuating there might be a substance abuse issue.

She and Barbie are currently in Norman, Oklahoma and are due in court Tuesday. Nick wants a judge to hold Heather in violation of their agreement.