How can you p a mouth swab drug test in 2 days?

PLease help! DCF is trying to take my friends grandson because of allegations made that were not true. The deal is she smokes weed and if she fails the test they will take the baby. Also, does she have to take the test if it is not court ordered? The baby is well taken care of ,plenty of food in the house and the first DCF lady said it was unfounded but this lady is determined to make this bad! Any suggestions would be appreceiated.