Well the lighter the bullet the less recoil so try a starting load from your manual on a 120 grain bullet. she is just after a doe and chances are you are going to try and get her relatively close for the shot.. That is that i would do.
I purchased the Remington low recoil 115 grain ammo (not quite into reloading yet) for my wife to hunt this last year. She shot a buck at 85 yards double lung (and not high either) and we found no blood until where the deer dropped which was approx 60 yards away. Not much expansion at all from these rounds. Something to consider when loading a slower, low recoil round. If you find a good bullet/load combo, let us know. I'd love a good one too.
We load 130's in all our 270 win's but painfully hot so that info is of no help but I have been tinkering with the Barnes 110TTSX in my 270WSM and the recoil of them going 3700+fps is way less recoil than a 140 Accubond going 400fps less. If a guy ran them 3200fps out of a 270 win I think they would be real mild but still be going fast enough to ruin a deers plans for the day.
Through an Edwards recoil reducer in it, cheap and simple recoil reduction, really takes the sharpness off the recoil.
does it have to be 270 WIN, since 270 win loaded with 130 grain bullet has more recoil then 308 win loaded with 150 grain, there is probably a way to load subsonic, I never tried it, but I think Lyman 122 grain cast bullet loaded with 35 grains of IMR 3031 should produce very mild recoil and about 2000 fps
The printed 2009 Hodgdon Annual Reloading Guide has an article in the front on low recoil loads by Ken Kempa. Here are the low recoil loads he lists for the 270 Win, and the recoil reduction ranges from 47% to 56% (to 8 to 9.6 ft.lbs of recoil) with the 110gr bullet.
Using 110gr Barnes TSX with 23.6" barrel.
1. H4895 43.5gr 2837 fps 1966 ft.lbs. 0.85" group at 100 yards
2. H4198 36.4gr 2815 fps 1936 ft.lbs. 0.97" group
3. IMR4895 42.9gr 2649 fps 1714 ft.lbs. 0.84" group
4. IMR4198 34.8gr 2701 fps 1782 ft.lbs. 1.20" group
Using 130gr Barnes TSX 23.6" barrel
1. H4198 37.4gr 2712 fps 2124 ft.lbs. 0.51" group, 42% recoil reduction with 10.4 ft.lbs. of recoil
You could try to load 130 grain bullet with 43 grain of Varget or 40 grain of IMR 3031, once I did try RE-15 on 270 I used 44 grains of it, wasn't bad, but I was only experimenting with RE-15, it produced nice .7" groups although...
I dont know hot to reload for subsonic shots, have never done it. Probably that is a good idea.
I reload for my 270 Win, it is a Winchester Mod 70, Pre 64, FEATHERWEIGHT, and my wife shoots it without a problem. My wife is 5 feet, 8 inches, tall, weights 120 pounds, tall and skinny lady, and she handles it perfectly fine. It is a very light rifle, which has a harder recoil than a heavier rifle.
I use 130gr, Sierra ProHunter, with IMR 4831, 54.5grains.
Hope this helps.