You are very kind to help your friend out in this way. It's a coin toss really. But if it were me, I would ask her to hold the sheet up to the light and if she can see through it to read a newspaper as they say, then I would voice my opinion about backing it with another sheet altogether, or fuse one to it. Maybe if part of the "Alf" sheet isn't as worn as the other parts she can cut blocks or strips from it to fuse to another sheet for backing? I'm sure she will appreciate all of your honest opinions and help.