Well, you obviously hit bone somewhere. There's no way a just-lung-hit arrow is gonna stop like that, not with the kinetic energy you should be delivering with that poundage and at that distance. What did it look like when you dressed her? What was she doing when you 'finished' her? Did the arrow pull right out or did you have to wrench on it to getit out?

It looks just like a spine-hit I made on a doe last year.