You've gotten good advice - and like others said, its hard to find a big box store that really has any idea about "Trap" specific guns / or any clay target guns for that matter ....
My favorite Trap gun - is a Browning XT with an adj comb / but even in 30" barrels it's a 9 lb gun ( and personally, I like the 32" a lot better than the 30" barrels ). 5'2" isn't tall - but the question is how much upper body stength does she have ? Mounting, swinging and following thru with a 9 lb gun / if she has relatively short arms and not a lot of upper body strength - is probably going to be a problem. But used / you can find some XT's in the $ 2,000 range ( they list now for about $ 3,100 ).
http://www.browning.com/products/catalog/firearms/detail.asp?value=008B&cat_id=013&type_id=057
For your wife - I think ideally you probably want to keep the gun in the 7 1/2 lb range / maybe 8 lbs max ....but you can judge that by letting her borrow and shoot a few guns at your local club. She'll identify quickly what suits her and what doesn't.
I think you're going to need to look for some semi-auto options / to keep the weight manageable for her - and keep the gun versatile enough to maybe fit you as well. A versatile gun I like a lot is the Benelli Super Sport, synthetic stock, comfort tech recoil supression system in it - and they make it in 12 and 20ga ( the 12ga is around 7 lbs / the 20ga is 6.2 lbs ). Its a gun that I use for some of my grandkids / as they approach 13 yrs old or so - still have limited upper body strength .... and both the 12 and 20ga are guns they like to shoot. In my 12ga, I load a shell with 7/8 oz of shot at 1200 fps - and it cycles the gun just fine / gives the kids a little less recoil.
Benelli Supersport ( not the Sport II - its a different gun )...
http://www.benelliusa.com/shotguns/benelli_supersport_and_sport_2.php
Most semi-autos don't come as a "Trap" gun configuration / but some of that is marketing vs reality. The idea on Trap targets is to shoot them as they are rising / so most of us like a Trap gun that shoots a little high ( like 70%/30% on the pattern's point of impact ). Some guns have adjustabilty / and some don't ....but you can shoot Trap with a gun that shoots 50%/50% patterns as well - you just have to cover the target vs float it over the barrels ...
But look at some of the other semi-autos as well / like a Beretta 391 - and if you can keep the gun around 7 lbs / it should work for you.
Its not a "Trap" gun specifically - but the Browning BPS Hunter model, with 28" or 26" barrels is a good solid pump gun.
http://www.browning.com/products/catalog/firearms/detail.asp?value=011B&cat_id=012&type_id=211
They do make a BPS Trap - but its a heavier gun ...and probably too much weight for your wife ( or, if she can handle 8 lbs plus / then go back to the Citori XT Trap models ).
http://www.browning.com/products/catalog/firearms/detail.asp?value=011B&cat_id=012&type_id=242