Jenelle Evans ' mother, Barbara , seems like she's ready to fight tooth and nail to regain custody of her grandson, Jace ... despite a judge denying her request for emergency custody. According to docs -- obtained by TMZ -- Barbara beelined it to court on Friday ... filing a motion seeking full custody of the 16-year-old, who is currently in a mental health treatment facility . Sources with direct knowledge tell TMZ ... the motion was filed behind Jenelle's back ... and it was quickly denied.