Does a mother have to testify against her daughter in a child custody suit in FL?

If the daughter's ex husband is suing her for full custody and his attorney has subpoenaed her mother as a witness in the case, she has to tell the truth to any and all questions asked, regardless of whether it's her attorney or the child's father's attorney asking the questions. So if any of the answers are answers 'against' the daughter, then the answer would be yes, the mother does have to testify.