Honestly, I think you may regret selling a girl that you've had for a while that is SO close. Plus, selling her as a near breeding sized, yet picky eater may not get you close to the value you put on her. It's entirely possible(that I've heard of) for a picky eater to go on and breed and entirely change feeding habits afterwards.
x2 ive heard that before too.
Weight is just as important as age. If shes 3 years old or older and at that weight i say go for it and try to breed her!