"I do know" in the third person

[Violino]

It's late, I can't sleep and... some thought about grammar has come to me;) As follows: if for example somebody asks me whether I know something, I know it and I want to strenghtening the answer - instead "I know" I can say "I do know!", am I right?
The proper question is how it would be in the third person? "She does know"? "She do knows", "She does knows"?

Thanks in advance as always;) and really warm (because in Poland is such cold nowadays :? ) greetengs:)

[Diverhank]

As with everything else, this should follow the basic grammar rules. --> She does know.