My niece trusts me more than her mom

My niece told me she trust me more than her mom. Doesn’t want to talk to her mom about anything personal such as her period, boys or anything she personal that she may should share with her mom. Her mom was in attendance when this conversation happened and I saw the look on her face when her daughter said those words. I told my niece you should never feel like you can’t talk to your mom. She’s your mom if she is not available then come to me but your mom is first and she told her mom sorry I just feel more comfortable with titi. I want titi with me when ever I need to be somewhere personal cause I trust her judgment more than you. Like how should I feel. Should I feel bad. Should I talk with my sister in law one on one. I do not want her to be mad with me. Her brothers are like that too. They’ll call me or come to my house and say titi I need to talk. Like I always made the open door policy like if you need me I’m here but I’m starting to feel my brother and his wife will start feeling some type of way as in why my kids always talk to my sister than me. Idk what to say. Any advice is appreciated