One of my Audis is a 2010 A4 avant with the same 2.0L TFSI turbo, with 126k miles.
@scott43's advice is spot on. Mine had the oil consumption issue and it failed the stage 1 test so Audi paid for a partial engine rebuild at 60k miles, which works very much in my favor and the car has been rock solid since. I have several higher end Audis but the A4 is my go to everyday car, and I think your niece will think the same of the A3 if she gets it. As
@Mazama said, find a good independent Audi mechanic and have him give the car a thorough going-over. These are really solid cars with proper preventative maintenance.
Without knowing options and trim level (premium, premuim plus, prestige) its hard to evaluate the value, but NADA pegs the average retail for an A3 with that mileage at $7800.