my two cents

there is no point discussion if Taiwan is part of China, this is politics.  Not suitable for office.  but if you want, you can make a stance.  
You could say:"of course, I don't need to feel responsible, because you are really just over-generalizing from one incident.  BTW, in my opinion, Taiwan is part of China.  But, that is OK, we don't need to agree on that. smile smile...
What she said dose not make her a bad person, but she is ignorant to make that kind of remarks in public.