My daughter and my niece both started shooting when they were about 6...they both moved up to Weatherby Vanguards in .243 (youth stocked) when they were about 7 or 8...great caliber and very good rifle. I have several .243's in the safe and my wife has shot a couple of them (she's not a very big girl, less than 120 pounds...) and she really enjoyed them and wasn't bothered by the recoil...I also have a 7mm-08 (Savage Model 11) that is actually pretty scary light and I figured that would increase the recoil...it didn't and is very manageable. As someone else mentioned, 25-06 is also another good deer option that is light on recoil, although I think they are heavier than the 243 and 7mm-08. If you don't reload, ammo availability is a little less available for the 7mm-08, but not scarce by any means. Both cal's will kill plenty of deer...

I would suggest you have her fondle several rifles to find one that fit's her well...look at the Savages (especially ones with accu-triggers) in Model 10 and 11 (110 and 111's too), Browning A-bolts, Tikka's, Remington 700's, Weatherby Vanguards (which is a Howa 1500)...all good guns for the money and will last a lifetime taken care of properly.

Happy hunting!