Three of my favorite things--irony, grammar, and Lost--come together in this from one of the many interpretive sites:
Explain the Lorentz Invariant for we English majors
Now, I don't want to get too technical, but I can tell you this: English majors modifies we, which is the object of the preposition for. So the correct pronoun is the objective pronoun us. I'd be willing to bet that she said "we English majors" because she thought it sounded right.
But between you and I, it's not. I'm so bad.