Immature, spoiled, childish, etc... with a severe case of "Me" mentality.
that would be an attention hog, a narcissist person.
A Narcissistic personality
Here is a link so that you can learn about your friend's problem http://www.mayoclinic.org/diseases-conditions/narcissistic-personality-disorder/basics/definition/con-20025568
I usually just drop into the background.
sad arse hole