These can work together well be sure to stabilize all your pieces well. I would not use the flag in the quilt at all. You may want to frame the quilt and hang it on the wall for her instead. Be sure to wash all your t-shirts and the jersey first to be sure the colors are not going to run before you start be sure to leave enough around each part of your shirts for your seam allowances. I know these little things should be easy to remember but you have no idea how many people will cut a t-shirt and not leave enough for a seam allowance. With this being your first t-shirt quilt take note of the different stabilizer mentioned in other post this is very important. Be sure what ever fabric you are using as a sashing between each t-shirt is equal to the the t-shirt/stabilizer just in case you have to add stabilizer to the the sashing. You will be fine with the t-shirt and jersey in the same quilt. Have a lot of fun and show us when you are finished.