Car jumps during turns at 50mph

My girlfriend drives a Lexus 300 that her dad purchased for her. When on the high way and making turns greater than 50 degrees and above 55mph, it feels like the power steering keeps making the car jump out of the turn. Its not the normal force you always feel when turning, the car actually drives in that direction. Any suggestions as to what the problem is?

Would you happen to be driving over a metal gap in the road when this happens, such as where two segments of a bridge or overpass meet? If so, the "jumping" is just the momentary drop in the amount of grip the tires have when they roll over that smooth gap.

Does it feel like the wheel is fighting you toward the outside of the turn?

If so, its probably time for a belt or a power steering pump