Yawn. You have to understand that Trek probably employs more gnar-shredding, air-getting, beer-drinking engineers who are avid riders than Niner does. Just because they're a big company doesn't mean the people who work there don't care.

The Lance argument should be a non-starter. If you were sponsoring a pro team in the last fifteen years, you probably had dopers on your bikes. To single out Trek seems a little harsh. I know that "everyone else was doing it" is not an excuse but it is the truth.

FWIW, I don't work at a shop that sells Trek, I've never ridden a Trek and I don't know anyone who works there. I just hate using the anti-corporate angle selectively against "uncool" brands. Niner is a company too. Use the "uncool" argument if that's what you mean.

To the OP: Tell her to ride both bikes (or the closest version the shop will order without commitment) and pick the one she likes best.