Is it normal to want a mother figure?

My boss a I have become really close over the years I've worked for her. She treats me like her own daughter and she's told me she loved me before when I was going through a really hard time. She always wants me to confide in her when I go through difficult things. I wrote her a thank you letter and I want to give to her. I feel she could be like a second mother to me. What's the definition of a mother figure? I have a mother but is that term only used for people who don't have mother's? I need a definition to use that shows a mother like relationship, would a "mother figure" term work since I have a mother?