Thats the exact model I was looking at. I was hesitant on the 6.5 Creedmoor, my daughter shoots my Desert Tech in 6.5 but it's on a tripod and suppressed when I'm not in Kalifornia. I like some of the set ups that have been suggested. Good excuse to build out a new rifle, "it's for the kids." That's what my wife says when I see Target, LuLu Lemon, and Nordstroms on her credit card bill every month... and she wonders why we can't remodel the house...
Don't be leary of a heavier profile barrel and/or rifle = helps reduce recoil as you already know
I run a pig saddle on my tripod with whichever kiddo is hunting with me.
Does the T3X lite have a thick enough barrel for a can?
I'm sure you're already thinking of most of this, just throwing out ideas because I know I can overlook things sometimes.
I would ask what shooting experience does she have.....but this isn't always indicative of how well a youth can shoot. Sometimes some pick it right up and others take more instruction.
Caliber wise........that also depends on her....shooting anything suppressed takes away concussion and then weight of rifle will dictate how much felt recoil there is.
Either flavor of 6.5 in CM or PRC will serve you and her well most likely.
If you went custom or snagged a rifle you could easily swap bolts/barrel....you could always go 6.5CM now and 6.5PRC later.
6.5CM is the main caliber in my stable but wanted to see what 6.5PRC is all about.
Hornady 6.5PRC 147 ELD Match shoots amazing in my son's rifle and performed well .....was only about a 50 yard shot though.
In my long 26 in 6.5CM bolt rifle.....I handloaded 147's and got 2868fps.........the exit wound on a whitetail at 632 yards was the size of a softball.....was quartering away slightly.....entered behind right shoulder .....exited left shoulder
Just throwing in that 147 ELD's have performed well on deer in 2 different calibers for me.