With the very short stub of a tail seen on many Rottweilers, what you're describing could be an infection in the folds of skin below her tail. However, I'm thinking that you are talking about an impacted anal gland which has abscessed and is now draining some bloody discharge. There are 2 anal glands located along the lower part of the anus, at the 4 and 8 o'clock positions. When an anal gland gets impacted, it can look like a good-sized "bubble"....
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