Seriously, I did not understand how Andy was supposed to be making the "right" choice at the end. Was she wring to screw over Emily? Maybe, but she tried to make it right later.
The first part, where Andy learns not to act like the fashion industry is all superficiality and worthless was GREAT and I say this as someone who doesn't care much for fashion. She assumed herself above her entry-level position because of the line of work—bad idea, and she deserved the call-outs she got for it.
Her friends and boyfriend, not so much. I can understand missing that one important thing with her boyfriend being a strain, but the rest of the time they're essentially telling her to stop doing her job well because it takes up time. Most first jobs are time intensive, especially in industries like publishing. Complaining about the nicer clothes—hey, maybe Andy likes them and is trying something new? And defending themselves with saying she never cared about fashion "before" is weak since she's working for a fashion magazine!
All in all, Miranda was bitchy, but also ran the top magazine in New York. Andy changed, but to fit a job with great opportunities and hopefully pursue a lucrative career. Why is that bad again?