If your gut feeling already 'knows', why do you ask the tarot? If you asked, probably you ain't that sure.
But now that you've got two answers, it's a matter of choice. Karma won't punish you because you didn't follow what the tarot said - the cards let you know something you might not have noticed, but it's your choice to do something about it...or no.
For how long have you known this friend? Sometimes, when we have just met someone, whe think they are the nicest people ever. But time passes and it shows us that it might not be exactly like we thought...though it DOES NOT mean this person is unworthy your affection. We need time to be able to clearly see the good and not-so-good sides of our friends. And i believe that, in a true friendship, we do recognize what the person has that doesn't really appeals us - we just learn to accept that as a part of the other's personality.
Maybe the tarot isn't giving you such a bad picture as you describe. Maybe it's only telling you this person is not all great like you think. And it's not bad, since noone is perfect. Just helps you to avoid illusions about someone else.