Is fishtailing on a wet highway more likely in a FWD car than an AWD car with the same tires?

I doubt AWD would have made a difference versus a FWD car in this scenario. Likely what happened was hydroplaning due to too fast for remaining tread depth on the tires versus the volume of water on the road (or on summer-only tires below 40 degrees Fahrenheit, but limited tread depth is more likely), and she may have panicked and lifted off the accelerator. In a curve, lifting off the accelerator can result in oversteer (specifically "lift-off oversteer") due to the weight transferring from the rear tires to the front tires. This also transfers _traction_ from the rear to the front tires, which can cause the rear to break loose first and the car will start to rotate. Another cause may be the rear tires having less tread depth than the front tires and/or the front and rear tires being different brands/types. I had a car I bought used with mismatched front and rear tire brands, and it REALLY wanted to oversteer on wet and icy roads, even when going straight, and both sets of tires had plenty of tread depth. Replacing the tires with a matched set fixed the issue completely. Oversteer means the car turns further than you have the front wheels turned (also known as "rotation"). Fishtailing refers to oversteer in alternating directions, usually caused by corrections in the steering wheel that are too slow (being "behind" the car). By countersteering (turning the steering wheel in the opposite direction it was when the oversteer started, aka "steering into the skid" because you're steering the direction the rear is moving) too slowly, drivers generally have to countersteer further because the rear is further off the midline, then the car will finally start rotating the other direction, and the steering wheel needs to be turned back further and VERY fast back to center or else the car will oversteer in the direction the wheel was turned. This can make the oscillation (the "fishtailing") worse and worse until the car spins. I don't think AWD would have helped over FWD in this situation. The problem is almost certainly due to tires (either not enough tread depth, unequal tread depth between front and back, mismatched tires, or running summer only tires in cold weather) though having alignment checked is also a good idea because some cars are _extremely_ sensitive to a bad alignment. Actually, there may be one difference between AWD and FWD...going downhill, if she wasn't in the accelerator or the brakes, the front tires may have been trying to slow the car down/hold it's speed with engine braking. It's possible that only braking the front wheels may have contributed to the spin, and AWD may have made a difference. Accelerating also may have helped in the FWD car as the front wheels may try to "straighten out" the car, but this is counterintuitive. I've slid down a steep icy hill in a FWD car and had to keep feathering the accelerator to keep the car straight (I had crappy tires because I was in high school and didn't know any better). iMO, tires make a bigger difference in a car's stability than any other single factor. I'd take RWD with good winter tires in the snow over AWD with garbage tires. They make that much difference.