If I am unmarried, living with my child's mother for the whole year the child was born I am directed to select "no" and choose how long, do we both choose the whole year?

the tip says "what if [child] lived with both parents, but we are not filing jointly" the tip continues to say if the parents are unmarried but still lived together the whole year to select"no" and choose how long the child lived with me. would I choose the whole year and when her mother files her taxes she would also choose the whole year? I am the one claiming her.