RE: 410 question...
If you kill a deer at 100 yards with a 410 and factory loads it will be luck. I honestly doubt if you could hit anything that far away with any consistancy any way.
If you ever held a 410 slug in your hand you would think twice about it.
Like I said, I own a winchester 410 that is actually built to shoot slugs. Has scope mounts and an open choke. If I considered shooting a deer with it (which I might) I would not take a shot past 50 yards and it better be a really relaxed deer at that distance.
I would also shoot the gun all summer to see what it was capable of as far as accuracy and range. And I have been hunting deer for 8 years with bow, muzzle loader and shotgun. And been shooting guns for 30 years. I am not a beginner. If you think you are going to go out your first year deer hunting and drop an average sized deer with a 410 at 100 yards you are deluding yourself. You might get lucky and connect with one in the vitals. And if and when you do you better have pretty decent tracking skills because it would be a safe bet that it won't drop where you shot it.
I also agree about the rifle. If centerfires are allowed where you live get a .243 or 25-06 and don't look back. She will LOVE either one. They are mild on reciol, flat shooting and usually very accurate. More than a enough for deer out to 200 yards as well (with the right ammo).
Your wife is plenty big enough she can handle a 20 ga at least. And if you add a bit of weight to the gun and a good recoil pad it will be even better. When I was a kid I shot a H&R 20 ga, which is a pretty light gun. I weighed about 80 lbs and was probably 5' tall. 3 inch magnums were a bit rough, but nothing I couldn't handle. When I was bit older I got a 30-06 for target shooting. (I only weigh 130 ish now)
Best bet for the money is the 20 ga H&R Ultra. Very nice guns for under 200 bucks if all you want to do is shoot deer. And like I said a nice .50 inline would be good to. They tend to be a bit more accurate on average than a slug gun. Some of the slug guns are pretty darn accurate if you find the right load though.
Paul