My brother in law owns a 83 Le Tour he bought new and nothing has been upgraded. It uses Schiwnn Cro-Mo dbl butted main tubing (but I would have to look to get more info if your interested). It also used Suntour VGT derailleurs which were middle of the line Suntour and a Sakae crank and bottom bracket along with Dia Comp brakes and Araya AL rims (can't recall the hubs but can look if interested). Schwinn also had a habit of buying whatever manufacture could offer them the best price on a particular part so parts changed every year. The bike overall is heaver than mine and mine has Renolds 531cs tubing, so the weight of 16 pounds does not seem remotely possible. My 531cs in racing form with tubulars, short stem, lighter racing seat, CF fork and handlebars would probably bring the weight down in the range of 18 pounds maybe high 17 range but that would be pushing it. And carbon wheels are actually HEAVIER than standard tubular rims, its the aerodynamics that is better with CF wheels at higher speeds- but they are also less reliable.
The bike your interested in has been upgraded after the early 80s. The question is how much is the bike worth? How much is she asking? Have you rode it to make sure it rides well and fits you? If outfitted with Campy components which ones and what % of the components are Campy? Just the derailleurs? or all the components? or something in-between? Personally I would not pay more than $100 if it looked like it was in good to excellent condtion...especially knowing she commuted 25 miles one way for years, and what if anything do you know about the rust going on in the inside of the frame? Plus it sounds like there are a lot of miles on the frame and components.
Sorry for the negative spin. But if you really want a piece of bicyling history you need to be looking at Italian bikes with all Italian parts no newer than the early 80s. The only Schwinn that comes close to that league is Paramount, but some years are worth more than others and I don't have enough info to give you the best years.