My friend doesn't know her migration status.?

My Friend is a US citizen but her mom didn't register her she is now 20. She went to the county she was born at to get her birth certificate in the court house and that's when she found out she wasn't registered. Her mom wasn't really present in her life considering that my friend was in foster care and taken care by her grandmother for most of he life what can she do? I believe she has and SS# but I'm not sure. That's pretty weird hu?!