Well, the 243 will have the least amount of recoil if thats the primary issue. The 7mm-08 will have a little more recoil but is also more deadly on whitetails in my opinion. I have one and love it. Try and find someone who has a 7mm-08 and let her shoot it. I know thats a little trouble but it may save you from wasting money on a gun she is scared to shoot. I'm no recoil lover myself and even without a recoil pad my 7mm-08 doesn't kick too bad. With a good recoil pad its very mild at least to my senses. If she can handle it then I'd get the 7mm-08. If the 7mm-08 is still too much then the 243 is the way to go. Another good option to consider is a 260 rem. Recoil is a little less than a 7mm-08 but its deadly on whitetails as well. I wouldn't consider a 308 for her if this is her first rifle. Most 308's that I have shot kicked about as much as a 30-06.

One word of warning though. If you get her a 7mm-08 or a 260 rem you may like it so much that you may start leaving your 30-06 at home whenever she doesn't go with you.