The .243 is a great minimum cartridge for deer, with good 100 gr. hunting bullets, that is!
Sounds like poor shooting, and/or bad bullet selection!
I'm not trying to be critical, but you just can't blame a caliber, for poor shooting!
If its not the bullet design, have you taught her exactly where to aim for? Aiming at targets, is not the same as aiming at an animal! Many times new hunters, or people with "buck fever" aim at the deer, not a particular spot on the deer! Also, 127 yards and 200+ yards isstretching it for her first deer!
Get her back on the range, and practice too! Sometimes we do kids a disservice, by putting them in the drivers seat before they are ready to drive!