Without knowing her it's hard to say but if it were me......
I think I would introduce Karen to a few rifles at the range first..... she needs to shoot the gun before she owns it. If the gun bites her the first time, she's probably not going to want to shoot it much. I would want her to find the rifle cartridge combination that she likes, then buy it for her.
7mm-08, .308, .257, .243, .243 wsm and 6.5x 55 might be good choices, but lighter rifles tend to deliver more felt recoil than heavy ones, and what she thinks is too much recoil might not seem like a lot to you or someone else.
You mentioned you thought the .22-250 was heavy but you didn't mention the weight of that rifle. How far is she actually going to carry this gun?
I wouldn't want to by a rifle for someone unless they were sure it was the one they wanted.
You should be able to find a .308 for her to try and see what she thinks about the recoil. BCP made a good point about that .308 cartridge but she may think the recoil is too much with a lighter rifle.