Can I call you "mom?"

Okay kids....as most of my friends and family know, I do not have any children of my own, but I do have a teenage stepdaughter. I have been in her life for 10 years now, so basically you could say I am more of a mother to her than her own mother. She has always called me by my first name instead of "mom" or "mother." Which is fine, because technically I am not her mother. Today she asked me if I would mind if she called me "mom." Without hesitating, I said "Sure, why not? If that's what you want to do." Now, the two of us haven't always had the easiest of relationships, as is sometimes true in a case where the child's real mother is not in the picture very much. But I have always been honest with her and told her the truth. When I promised to take her somewhere or buy her something, I followed through. I've tried to instill in her a sense of responsibility and understanding that a good education can take you a lot of places. I never tried to take the place of her real mother, even though she is basically an awful person who only thinks about herself. So, I guess if my stepdaughter wants to call me "mom," it's okay by me.