Sorry to hear about your friend's loss. No suggestions on how to approach her. I personally would offer after rather than before. If she's still working maybe you could just talk about recycled shirt quilts in general now, then make the offer later. As far as how many you need, there's the ever popular 7 shirt quilt:
http://thethriftyquilter.blogspot.com/2009/06/seven-shirts-seven-steps-one-thrifty.html
Here is a recent post:
http://www.quiltingboard.com/main-f1...t-t239974.html
And here's instructions on how to deconstruct:
http://quiltville.blogspot.fi/2012/0...irt-movie.html