How do I deal with a friend who always thinks she's hard done by?

Whatever I tell this person, she always thinks I'm lucky and she isn't. Are there any websites out there explaining why people act like this and ways to deal with them? I can't tell her anything without her saying I'm lucky and that she envies me - even on the minutest thing! She moved flat with her mum (her own property) and she said I was lucky that if I got fed up I could move as well as my mum owned a house! Well, I'm not lucky as I don't own the house - my mum does. I feel I have to keep explaining to this friend all the time that I am in no way lucky. In fact she is luckier than me in that she has 2 older siblings whilst I'm an only child.