First, I want to say that I understand why you're speaking in third person, but it is still really annoying and I doubt it will help you prove the point any better. I don't know your SO though.
Secondly, Partner 2 is not only selfish, but an idiot. Partner 2 making $30,000/year is taxed at 15% while Partner 1 is being taxed at 25%, and once you throw in the deductions for your "significant" student loan bills, Partner 1 and Partner 2 are making very close to the same amount. Certainly not disparate enough to warrant any significant difference in rent being paid.
Fair is fair. You're both get the same thing, you both should pay the same thing. Sounds like Partner 2 has a case of trying to keep up with the Jones', and not only that, wants Partner 1 to pull their weight too. I'm going to go out on an extremely sexist limb, and guess that Partner 2 is the female.
