From some random web site, so no reason why it would be accurate but matches information I had previously gleaned:
"In September last year, during a Jessi Combs exhibit at the famous Petersen Automotive Museum in Los Angeles, Combs? team said they had filed for the posthumous record, since Jessi had been able to perform the two mandatory consecutive runs before crashing. Also then, they said she had averaged 531.889 mph (855.9 kph) from the 515.346 mph (829.3 kph) and 548.432 mph (882.6 kph) runs, topping O?Neil?s 1976 run at 512.7 mph (825.1 kph).
Guinness lists the current record at 522.783 mph (841.338 kph), which is lower than the previous figure but still over O?Neil?s. Jessi?s longtime dream has finally come true."
This seems to say her fastest one-way was 548+mph and she had a two-way average of 531+mph.
So where does the Guinness figure of 522+mph come from???