I wish she could be a pet for someone, but the most humane thing to do is cull them not too long after they reach processing age. Otherwise their health declines and they have pain and eventually probably a heart attack. At 16 wks, she'll probably need to be pressure cooked, but will still be really tasty and delicious.
She's had the best life she possibly could with you. Much better than any life in a factory or a cage. Lots of fresh air and grass and inter-chicken interactions. Her life may be short, but it's been of excellent quality. Sorry she couldn't stay with you and be a pet.
I usually see what whole chickens sell for in the grocery store per pound, and that would be my starting price for her. A dressed carcass (the whole hens sold in the store) is roughly 2/3 the weight of a live bird. So 14*.66 = 9.24 lbs dressed. ~$1.70 / lb for whole chickens where I live. $1.7*9.24 = 15.7 So the lowest price I'd ask is $15 for the live chicken.