She is doing that because she is gravid and will lay eggs in the next few days.. The inverted position is pretty common in gravid boids.. They often get pretty contorted and come pretty close to a pretzel.. They MAY do it for basking the belly eggs/ babies and I also think they do it to get the eggs/ babies situated for delivery.. From what I see it gets more prominent and intense just prior to delivery..
BTW, Borneo's ARE awesome and yes they are KINDA like stubby burms.. BUT if they were to reach the length of burms they would beat out the anaconda for the heaviest..![]()