I've read the entire thread. I've never posted till now (check my IP).
Although almost anything is possible, but if there was no bib swapping or simple error on the course (shouldn't have been based on the map that I saw), there is very little chance that the lady in the picture (assuming that it is actually her), averaged that pace for 26.2 miles.
Throwing in the fact of her running around 5 hour marathoners at some point in the race, it becomes as close to impossible as it can get.
Human error or not (I don't know what the truth is), I've never seen anyone with a body like that anywhere around 3:11 marathon pace.
In addition, her being female, her age, and not having pr's at shorter distances at that pace or faster raises huge red flags.