I use to think the same thing about my boyfriend. He could have anyone he wants, but he chooses me. I'm physically disabled, a drug addict (3 years sober this month :'D), a great source of argument with his loved ones, an actual source of discrimination XP, I'm poor so I have to mooch on him too often, sex has too many weird restrictions, I lived 300 miles away in the beginning of our relationship, he's never had to work so hard to keep someone alive, and overall this whole ->-bleeped-<- is stressful XP. He insists that I enrich his life though, and that this whole mess is worth it. It'll be 4 years together this month, and he refuses to give up. After a while, I decided not to give up either.
So do I think your girlfriend is too good to be true? Nope, I think you just found yourself an awesome girl who sees the real you and sees how in the end you're worth it all.