Mark, you may be too far along for this, but she considers your pieces art. If you do undertake this commission, then you need to charge like it is art and you need to do it at an artist's pace - ie. over a long period of time. Also, art is not rushed. If you took a year off between pieces to clear your mind, she should be understanding about it.
Otherwise, pass. People should do what maximizes their value. I should not be rebuilding a transmission on a car just because I can if I can do my "job" for more money.