I am not Native American, but I have worked with a tribal group for some time. I would suggest that you ask you friend to provide you with some of the symbols of her tribe. For instance the group I worked with used the turtle as one of their traditional symbols. Another source is to view any of their tribal publications. magazines, newspapers, (all online these days) notices on signage near their reservation. There you will find accurate traditional symbols. Most are stylized interpretations of natural objects that could easily be used in a quilt. In my area of Michigan the tribe also celebrates babies in the spring with a strawberry festival and ceremony. (Berries are the shape of a heart) so using strawberries would be appropriate as a symbol or part of the quilting itself.
But in the end to be accurate and sensitive, ask her tribal name and region. Contact the Cultural Department on one of their reservations and you can gain a mountain of information about appropriate use of symbols. You are on a cultural journey. My one caution is don't give her a southwest inspired quilt if her tribe is from say, the mid-west or northeast. It might be well meaning but not sensitive. I would be like giving an Irishman a quilt covered with fleur de lis.
