I agree with the commentator. It seems the OP was quite full of herself. Speaking as a "country bumpkin from a working class family," I wouldn't be surprised in the slightest if the OP's opinion of where Suzanne came from was coming out in her treatment of her. It almost seems as though the OP thinks that Suzanne SHOULD feel inferior to her, so naturally that would be what her problem is.
When I was working on my BA, I lived with two girls from wealthy families. I met the first one through my now husband and we didn't like each other at first (not because of class differences, but because of a misunderstanding and lies that a now mutual enemy was telling us about each other...we were naive college freshmen, after all). After a while, we became really good friends...I actually didn't know she was from a wealthy family until after we had both graduated and gotten married. She had a good head on her shoulders, she was a hard worker, and she didn't act spoiled or superior to me. We're still good friends (actually, we're seeing each other next week for Thanksgiving). The second girl, however, was the rich-girl stereotype you often see on TV. She flaunted the fact that her Daddy could buy her expensive new cars every time she wrecked hers because she was doing something stupid. She'd get offended if I told her I couldn't go out to dinner one night because I couldn't afford it (I really couldn't!). She had no idea how to hand wash dishes and got confused over the dish drainer and she flipped when her parents wouldn't buy her a ticket to Vegas for her 21st birthday. She was terrified the first time she heard a cow moo because she didn't know what it was (which has always confused me, because that's something you learn at, like...age 2--"What sound do the cow-cows make?" "Moo!"). Second girl and I did not get along. Hell, first girl and second girl didn't even get along.
The point of that story, though, was that the attitude each girl was what mattered, not how much money she had. It IS possible that Suzanne doesn't like the OP because of her background...but it's more likely that it's because of the attitude she seems to have about her background making her worthy of Suzanne's envy and feelings of inferiority.
HOWEVER, I was never outwardly rude to Second Girl. I kept things civil and then we mutually and cleanly broke away after we stopped living together. Suzanne was EXTREMELY rude. While she may have had a good reason for not liking the OP, there is no excuse for the email she sent or the gift-grabbing she did.