She is way too young and inexperienced to take that on, and nobody older and more experienced than her will step up.

When I was a kid, I didn’t know a darn thing about the Catholic faith, and I thought that someone being a «Godparent» meant that they would take care of their godchild in the event of their parents’ passing. The concept of a godparent only being a spiritual guide for their godchild did not register with me. 

There is a vast difference between spiritually guiding a child, serving as the main family babysitter, and taking on the full responsibilities of parenthood. The latter is something you should not take lightly, even if the parents in question are young, healthy, and very unlikely to both pass away. It’s not the kind of thing you should hastily agree to just because you were asked and you fear there’s nobody else who will take on the responsibility. You don’t want hypothetical childless kids to end up in foster care, but you also don’t want to agree to care for them when you yourself are not fit to do so.