The sales stats released in the industry standard trade magazine does not back up her claim. There is no evidence to support what she is saying. It might be true, but she might also be overestimating/overstating the game’s success. People tend to be proud of what they create. So, you will have to color me skeptical.
Of course, but you also think 4e was the best edition of DnD and thus the best seller. Certainly would affect your perception, wouldn't it?
1) She does say it took a while for a careful magazine industry to say what she (and probably WotC staff) already knew.
2) Paizo didn't make this public until two years after it happened. Shows they are careful and do not want to antagonize fans or try to profit from such info (in a we are better than you are way). Unless you think this statement being loss in a blog is all part of a devious marketing strategy...
3) Icv2 tied DnD and Paizo for first place in the 2nd quarter of 2010 (or was it 3rd quarter?). That is an independant source and happened before PF, according to Lisa, out sold DnD. It's not just her word vs. your disbelief check. Seems the standard mag industry does back her claim.
4) It takes a year (average) to produce a DnD book. This means Essentials were in production in 2009, when Pathfinder only started being released (august 2009). Everyone agrees that Essential was done to recapture people who left DnD because of 4e, so already we see that WotC didn't get all the fans and market shares it wanted from the release of 4e before PF was even released. It's not a stretch to think that PF profited from people who didn't like 4e and that 4e wasn't very popular, making it easier to "outsell".