My best friend keepings wanting to see or connect with her mom but her mom wants NOTHING to do with her and she gets hurt. What do I do?

If a parent doesn't call you, visit, or even make an effort to say, "Happy Birthday." to a child, should that person just cut all ties from that parent?
That's what my best friend told me what her mom did. She was heartbroken that her mom didn't wanna talk to her when she wanted to wish her a "Happy Mother's Day". She always has her hopes up when she thinks her mom will turn around. I feel so bad for her because she doesn't have a mother. I mean it's sad. What should I tell her?