score:9
The answer has to be no, because there was wasn't solid evidence that it happened at all, until recent genetic tests essentially proved it. There were rumors, and his own suspicious behavior, but that's all we had.
However, there is one thing that is pretty clear: no matter what her feelings were on the matter, as an enslaved person, Hemmings was in no position to say "no". Withholding consent was not an option for her. That by itself makes the relationship rape, in the same way that a grown person having sex with a minor or mentally handicapped person is automatically considered rape.