It sounds to me that she was not warm enough to digest the rat, & also, after a snake has not eaten for so long a time, it would be best to feed on the small side.
Please don't rely on "feeling by hand" for temperatures...you need accurate measurements. We are roughly 98.6* which is way TOO hot for a BP, & their optimal temps. typically feel "cool" for that reason, but check!
BPs need about 88-90* in part of their cage to digest & properly regulate their body for optimal health. Even though you may have gotten away with 80* for some years, your BP isn't thriving this way, & this puts her
at risk of various illnesses.
Regurgitation can be very hard on a snake's insides: think about those rat teeth & claws that could cause internal lacerations...snakes have occasionally died just from regurgitating a meal, so it's best avoided by making
sure your snake is warm enough to digest & not fed something that is too challenging if they haven't eaten for a while and/or if their cage is too cool. I suspect that pain may have caused her to stiffen up. (it would me!)
Don't offer any food for 2-3 weeks after a regurgitation, & when you do, make SURE it's something small (!) & it would also be best to add some probiotic* powder (for snakes) to it also. (*BeneBac for reptiles, etc)