[RIP]

Could be any number of things causing it. If it's still under warranty, take it to the dealer.

Your clues are stalling while braking in turns and a whine. These greatly expand the possibilites. Tough to narrow it down. Are you getting a Service Engine Light (SEL) on the dash? Was any maintenance done three weeks ago to start this? Is the transmission shifting ok? Is it a smooth stall or does it jerk? Any brake problems like spongy or lacking response? You said when you idle through the turn it's ok. Does that mean whenever you hit the brakes it stalls? If so, turning may not have anything to do with it because most of us hit the brakes when slowing to turn.

First thing I would do is see if any fault codes have been stored. Two ways to do it but, the best way is to go to your local AutoZone and have them download the codes. It's free. Come back here with the codes and we'll go from there. Second, determine exactly where the whine is coming from. Maybe your friend can help with that. Third, if you haven't recently, consider change the transmission fluid and filter.

Your friend appears to be implying at least that the power steering pump could be dragging the engine to the point it stalls. Well...can't count it out but, the engine electrical controls should compensate for it. If that really is the case then that could mean you have a bad pump AND an idle problem caused by the engine sensors.

We could all come up with endless theories at this point. We need more facts to go on. The codes, or lack of them, are the first tool in the toolbox. Get the codes and we'll go from there. Welcome to the forum. Cheers!