Your boa is pretty. I'd agree that she's quite large for a 2 y/o but her body condition looks pretty solid so she's not too far gone. Moving to a 2-4 week feeding schedule sounds like an excellent plan. For comparison my 2.5 y/o male BI, who I've had since he was one, isn't quite 3ft and is roughly 1100g. He eats a small rat every 2 weeks but he'll move up to mediums in a few months at which point I'll scale him back to a 3 week feeding schedule.