.243 is great
There is nothing wrong with a .243, .223's are legal here with the right load (900 ftlbs @100 yds), but my 9yr old shoots mommy's .243 youth just fine and improving everyday! she prefers targeting with that .223 but when she gets her first tag next year, it will be the .243 with shots limited to under 200yds prone or under 100 in any other stance. we load 85 partitions, 95 partitions, 100 round noses and 100 flatbased sierras. LOVE IT have not tried the sierra hollowpoints but i HEAR great things and will be trying them soon. That said... we just purchased a .223 CVA hunter (break action) that i think might add a lil more recoil in a .243 because of the lightness of the rifle. Still a great gun period. If she might be shy...... a slightly (SLIGHTLY) heavier bolt gun might be in order. CVA does not have interchangeable barrels to my knowledge but they are 200 here. Rossi (i know not HIGH QUALITY, but functional) has interchangeable barrels so graduating calibers would be easier.... I THOUGHT Handi might but I'm not sure... If I were buying my girl a first time deer rifle, I would look for a bolt gun that fit her well and load it for the best round she could handle. If you don't handload, you can still find quality ammo in most places, still prejudiced towards an 85 partition at 250 yds and under. in bolt guns there are savage, ruger, weatherby/howa to choose from *EDIT* for quality price range reasons... obviously there are more options and these are just my picks*END EDIT*. I lean towards adjustable triggers and STOCKS when possible for a growing youth, my brother and I had to hunt with full size rifles growing up BUT we still use them regularly now! you can use either break action or bolt effectively, and with practice the break action can be loaded QUICK for follow up shots.... I would suggest starting with varmint loads for the target practice sessions and save the slightly more uncomfortable deer loads for deer season where (in my experience) she'll be too focused on watching that deer buckle to notice the recoil difference. Let us know how it goes, best of luck and wishes to another young hunter!