A.E.
I disagree on the age thing. I think it's her maturity level, not her age that is at fault for her not "stepping up." I'm 21 and I stay at home with my son everyday. I was in the NICU everyday from 8 am-11 pm until they released him. I dropped my classes because he was getting too sick at daycare and needed to be home so he could develop without complications (he was a preemie). I also have lots of people who would help me if I wanted/needed it. I live with my mom, and she has even offered to keep my son so I can move out and get back to school. I won't do it. He's not her responsibility, he's mine.
I agree though, that if she had no one to turn to she would have no choice but to sink or swim. Hopefully she won't end up neglecting her child, but I think the grandma should be less available because her daughter is obviously expectant of her help. Just make sure that when there is no one available for her to pawn off her children to, that she doesn't leave the child by herself or with shady people.
And if it comes down to the grandparents taking custody, that may be in the best interest of the child. My fiance's mother had that happen. She was 18 when she had my fiance's older sister and their grandma took the baby from her, adopted her, and probably saved her life.