I've been down this road with 2 daughters currently 9 & 11 yrs old.
Long story short 243 Win 80/85gr Barnes TSX/TTSX, 6 Creed 95gr Barnes LRX, or 6.5 Creed 120gr Barnes TTSX are my recommendations.
My then 10 yo shot her first 3 deer the year before last.
1st deer with a 6 creed 26' barrel 108 eldm @ 140 yards.
2nd deer with subsonic 350 legend 16" barrel 205 Maker @ 30 yards.
3rd deer with 6 dasher 20" barrel 105 bthp @ 185 yards.
All 3 were neck shots.
I regret getting AR's and building a 6 Dasher for them to start with because a 243 win or 6 Creedmoor doesn't recoil anyways. I hate that I got guns that were "perfect" for starter guns with "low" recoil when I found that they could handle a 6 Creedmoor just fine.
We shoot everything suppressed so the recoil and blast is reduced but even unsuppressed I wouldn't go smaller/slower than 243 win/6 Creed.
This year she shoulder shot a 9pt @ 104 yards.
6.5 Creedmoor Bergara Stoke
Barnes 120gr TTSX factory ammo
Chrono graphed at 2755 fps 20" barrel.
This will be their go to rifle from now on. She doesn't even notice any recoil with the suppressor.
