Because she's a mother... Mothers have unconditional love for their children and when they see their child is hurting or sad or any sort of emotion, they want to make it better for their child and perhaps her mother thought a hug would make her feel better. Regardless of how many times she's tried hugging her in the past, she's still her mother and I doubt her mother will give up on her and just stop trying to hug her. It's her daughter, she loves her.

I remember when I was in my severe depression, my mother would try hugging me and talk to me about everything and at times I just wanted to smack her and say, "Leave me alone!", because she'd repeatedly try and try regardless of how many times I'd say, "Please just let me be and let me figure things out on my own"... But I'm so grateful now that my mom insisted on helping me and never gave up on me. It showed how much she loved me and wanted to help, she never gave up on me. I think Miss_A's mother is trying to do the same. Just a thought.