I can think of 2 possible explanations:
1) She's just really stupid, or she expects that people won't fact check her lies. The reason that she makes them in the first place is because she thinks that they put her in a good light.
2) Some people just don't have a good grasp of reality. They often fail to comprehend what's going on in front of their own eyes. Moreover, it's been shown that human memory is highly fallible for all people, but for some people the past is more malleable than for others, and they often believe their own "mistakes".
Personally, I think explanation #2 is more likely; I would guess that she believes her own lies & doesn't care what so-called "fact checkers" have to say. But that's the diagnosis of one armchair psychologist analyzing someone he's never met.