Flattery and truth

Can something that is true and honest also be flattering? Should it? If you tell a really beautiful person that s/he is beautiful, is it also flattery? Perhaps the answer is determined by the person receiving the truth (I almost wrote compliment); if they don't consistently feel that they are beautiful, they might feel flattered... Whereas, if a person who is routinely told s/he is beautiful is told they are beautiful, will they and should they feel flattered? Is flattery always dishonest, to a degree?

I've never lied when I've told you that you are beautiful.