Andy is colourblind.
It's not that she literally can't see any colours, but that her colour discrimination is much worse than most people. She genuinely can't tell a cerulean sweater from a turqouise sweater, and that's why she has a hard time taking fashion seriously. Even in the outfit montage, she's dressing mostly in shades of grey, black and white. She might not even know that she's colourblind, and just assume everyone is making meaningless distinctions.Emily is anorexic.
The characters in the film engage in crash dieting a lot, but when people go on crash diets it’s a short term thing, usually to compensate for eg holiday weight or before a big event like prom or a wedding. Emily is always doing it. She also has signs of anxiety (understandable when you work for Miranda) which is common with anorexic people. She also gets sick constantly which is what happens when you’re anorexic. Miranda used a surrogate for the twins.
It's clear they're her daughters and they seem to be around 13. Miranda is presumably in her late 50s or early 60s making a pregnancy near impossible when they were born. Especially since she's in the fashion industry where gaining any kind of weight is heavily frowned upon. Miranda knew Andy didn't care about getting the job.
Andy was horribly awkward, didn't do any prior research on Runway or Miranda, didn't care for fashion and snacked on an onion bagel moments before the interview. She probably knew her odds of getting accepted was slim and gave it a half-hearted shot before moving on to less prestigious and less toxic backup jobs. Miranda sensed her lack of effort and gave her the job to teach her a lesson. Miranda hired Andy because she thought she was cute
Either in a romantic or platonic sense. Either way, Miranda gets bored of her about a week in and becomes more willing to fire her until she proves herself useful. Emily and/or Nigel are Driven to Suicide or murder Miranda after the film's events
