Legal Question in Family Law in California

You don't say what grounds he is basing his attempt to get sole custody on. There is no way either of you will be able to "take away" the child, unless one of you has or can be proved is likely to endanger her. Otherwise it will always be a balance between the two parents based on whatever the court determines is in the best interests of the child, starting from the presumtion that regular and frequent time with each parent is usually in the best interest of a child unless something proves otherwise.