While George is not very flappable when armed with his trusty portable video game console to avoid eye contact with, and in the company of people he tends to loom over, he can occasionally make the mistake of looking up from his games while close to eye level with someone. This gives him a penalty on his defense roll, and can result in him being flappable.

It's also possible that Rhea's just that certain of what she's saying.

Could be both.