Well I can tell you that she seems very happy and very content, she basically eats whenever she is hungry. She lets me know by coming up to the window on the tub and giving me the eye, usually when I'm cleaning the rodents, or she paces the tub. She doesn't look fat to me, just very healthy. Personally I think the skinny snake above looks a bit sickly compared to Lucy. I have read that any animal that is under fed to the point of being starved can live a lot longer than something that eats a lot. They say that if you want to live to 100 years you can starve yourself LOL.
To me that photo of the pure Jampea looks way overweight. I basically go by the body shape, when snakes are young they can process the extra food and put it into healthy growth. Once they reach that sweet spot where their metabolism slows down I'll reduce the food or stop all together. I have a King snake that got really fat and I didn't feed her for months until she was back down to a healthy weight. I also like to keep my snakes on the heavy side (not too fat though) for when they go on an extended fast, especially during breeding where they can fast for up to 6 months at a time. If they start that fast on the skinny side they end up so skinny that I fear for their health. I've also found that especially with retics that if you under feed them they can get super aggressive, especially during feeding time. The feeding response is crazy and can be very dangerous for the keeper. The more you feed them the more it mellows out the feeding response.