The TL/DR version: Sidewinder or FD
I think I might actually have some useful feedback, although I don't think it's going to be all that different than what's already been stated. My longest (level) shots in no wind are at about 280-300'. If there were no wind, the Leopard would probably be all I need, but this is reality, so sometimes I need higher speed discs.
People keep saying 'Sidewinder', and I mostly agree with that. A Sidewinder was my first real driver. It was a beat-up 170g champion and it was great, until I lost it. I replaced it with a Starlite (159g) Sidewinder, and immediately saw a noticeable improvement in distance. It' a good disc. In fact, the Starlite one i have is such a mellow flyer, that I could probably leave the Leopard at home, and still be able to shape the same shots with it, while ALSO having a disc that handles headwind a good bit better.
However, also maybe consider a Dynamic Discs Witness. I think it falls neatly between Leopard and Sidewinder. Both my husband and I liked this disc so much, we both got one (both in Lucid plastic). I only gave mine up when he threw his in a lake, and I had other options. So now he's bagging the one I had. It fills the same slot in his bag as a Sidewinder. I seem to recall mine was low-mid 170s in weight.
If I had to pick ONE 'perfect' disc though...Fairly recently, I added an 174g Discmania FD Jackal in S-Line plastic. I bought it used, but had I purchased it new, I'd have aimed for something like 165-170g weight. Otherwise, this thing is amazing. It will fly straight for days, with a minor fade at the end. It will hold an anhyzer line well, and do a fade about like a Leopard or Sidewinder, but it also holds a hyzer line pretty well, and its glide beats pretty much every other disk I've ever thrown.
I recently picked up a 172g TL in Star plastic, to compare to the FD. They are very similar in most respects, but I think the FD edges it out in Glide.
I started playing this year, and went through a LOT of discs (mostly used), to see what I liked. I had an Eagle, Teebird, Firebird, Saint, Assassin, Thief, Witness, Destroyer, Sidewinder, Dragon, TL, FD, Dragon, Archangel, not to mention discs that were ridiculously too fast.
What I BAG is a Leopard, Sidewinder, FD, and Thief. Leopard and Sidewinder are understables, FD is stable, and Thief is mildly overstable.
So, assuming she has no interest in an overstable fairway driver, my recommendation is the Sidewinder and/or the FD. And If I had to pick just one... the FD. And if you can get it mid 160s weight, all the better.