Heavy or light gun dont matter.
they all dont kick with target loads unless you have a bad shoulder. if it does kick, then use 8oz shots rather than 7 1/2.
I would recommand used browning citori or any used O/U gun. First, I would consider for you to find a gun that "FIT" you since sporting side of shotgun is all about the gun fitting your body.
If you are a member at local trap/skeet club, most of those people will have beretta 6 series, browning citory, and few semi autos for you to use and test. Some might even sell you one for good price!
I would personally never buy anything "Cheap" in O/U new in sporing or trap gun. I have seen few people with cheap CZ or mossy breaking their firing pins after few thousand rounds which is unheared of. Experienced guns that are known will still last you your life time if you take care of it.
BT99, Citori, Beretta 682 are some of many Known to last guns with their good reputation for O/U.
Beretta A391, A400, Browning Maxis, Rem 870,800. and more are known in semi auto world.
I personally collect most beretta O/U Trap and sporting shotguns and have had few Blaser F3 sporting, SV10, caesar guerini trap, and others to have fun with. The thing is... all those expensive guns are fun to shoot but i still shoot 10 year old bear up and modded Beretta A391 trap all the time because it fits me the best.
Hope you can shoot before you try it for any sporting, skeet, and trap guns so you know that it fits your body perfectly. if you find one, then she is a keeper and will play with her for very long time.
Let me know how much you are thinking of spending and straight, monte-carlo stock or sporting, trap barrels and i might be able to track one down for ya with reasonable price.
cheers and hope this helped little!