She is perfectly fine. Don't worry if she's small. Not only do boas have slower metabolisms, they often have widely varying growth rates. One boa at 1 year old might be 700gm and another might only be 450gm. She will hit her growth spurt soon enough. She appears to be in perfect condition. I would MUCH rather see a boa small and slender than big and fat. She will get big enough in no time. Just feed 1 appropriate sized prey every 7-10 days and she will do just fine!
And I still say a rat pup is fine for her for now. Just as feeding less often is better for these guys, so is feeding a slightly smaller prey item. Truly, it'll be ok!!
Note: don't know why that angry face is showing up in the heading of my post - sorry about that! I'm not angry, really! It's all good!![]()