oh i don't feel that your question was silly at all...i think you show a good perception about ppl that create a negative aura in our lives. i had to learn this in therapy so that goes to show how befuddled i was. i'd have something happen with ppl in my life and boom i would be so depressed. what i learned was coping skills to offset the depression and also that there were some ppl in my life that were not healthy for me.
my t told me to go with my gut instinct rather than second guess myself. i was always giving the other person too much of the benefit of the doubt. so as for your friend...it sounds like your gut instinct is telling you this person may not be a good thing to have in your life.
hope this helps and keep us posted, k? we do care for you.