Beautiful hypo mojave!
As for the size thing, I have some 2012s that are 800 grams and others that are 200-300. They all had been with me from very young and get offered food every 7 days. Some are pickier with frozen, but will still eat every 2 or 3 offerings. Some of the smaller ones will eat every time I offer, but they don't retain as much weight as some of the others. I wouldn't start saying bad things about a breeder or a way someone cares for an animal simply because they aren't 1000 grams at almost a year old. Every animal is different. Her body looks nice and full, so they were doing something right.
Not every snake will put on 50-100 grams a month. When I see animals that put on 200-300 grams a month it raises a red flag about the feeding that the owner/breeder is doing. To me, up to 100 grams a month is a nice steady (and slow) rate of growth. I'm all about raising them up slow and not cutting time off of my animals life. Just my two cents.