Who would Bush have known better? Killian's son or Mrs. Knox? Most secretaries worth their salt know a great deal about all sorts of things, so much of what she's saying sounds plausible to me. I'm not sure an 86 year old former secretary's memory would be as good, nor does the "even though these are clearly forgeries, they're right" give one much confidence. In the end, I think it all boils down (once again) to "he said she said", which is another way of saying "believe according to your ideology", which is the best that the Democrats could hope for, given that their guy is clearly a jerk both in the 70's and the present day.
But was she really a secretary or just someone in the typing pool at the base?