You are a Wonderful Sister In Law. With the patience of a saint, whatever you both do I'm sure will be Fantastic !!
Keep in mind at some point may have to let her know you think somthing just didn't go.... in a nice way! :)
All pieces chosen are Great !!
About as far as i go with asking someone what they like are, what colors do you like.
and of course will be watching for updates !!
Happy Quilting !!