Those were the wheels on it? If so, it's a 24" bike. The rim may measure about 20" in diameter, then add the tire height top and bottom, and you get 24". 24 x 1.75 rims is what you should look for. Most 24" beach cruisers today have that same size, so a donor bike will have tires, wheels, and other stuff that can go on your American classic bike. Look on CL for a 24" cruiser, probably pretty cheap in price.
The dropouts ID it as Columbia made, and the serial number should be on the left rear dropout. The letter it begins with will be a code for the year.
You should get it riding well, and then keep it, as a 24" girl's bike won't bring in much profit, even in excellent condition.