I don't recommend tents for the AT, although during the bug season they are useful. There are lighter ways of protecting yourself against the bugs, but a tent is easy. Once you get past the bug season, I would remember going with a tarp.Can I ask you your opinion on this tent? It would be for two people for the AT. I know you probably have not used it but maybe know what to look for.
http://www.rei.com/product/763437
Also, I have heard mixed things about the backpacks with the exoskeletons (I think thats what they are called) to distribute the weight on your back. What do you like?
Nevertheless, if you (or your partner) really want a tent, then aim for something around 2 kg (4.4 pounds). Get one you can set up easily and has good ventilation - the AT is humid!
I believe you mean internal frame (an "exo-skeleton" would be an external frame, which are almost impossible to find anymore). I recommend a light internal frames if you're going to carry more than 10kg (22 pounds). The frame should be so light that the empty backpack should weigh less than 1.4 kg (3 pounds). I recommend the Mariposa Plus from Gossamer Gear. GoLite also makes some nice lightweight backs with internal frames.
I used frameless packs for my three long thru-hikes, but I also rarely went over 10kg. When I did, I suffered a bit, because they don't carry as well as a backpack with a frame. However, most of the time, since I was under 10kg, I was quite happy not to have to lug around a frame.