Re: .243 loads
The 243 win is not marginal by any definition! There are so many great choices out there for her, I would personally consider her build and attitude before anything else. The last thing we want to do is scare her away. I would assume her 243 is a 1-10 twist, as most are these days, pick a bullet in 85g and don't chase speed at all! Keep the bullet light and the powder on the low end. I would suggest a TSX, TTSX, ACCUBOND, SST, NOSLER BT, Sierra SBT, man the list could go on and on for mule deer inside 300m.
Remember this experience is going to be seared into that little girls brain for the rest of her life, girls don't forget like little boys do.