Still, with that many livebearers, one girl won't be able to take care of all those fry. It sounds pretty well stocked, so I don't think you should add anything else. You'll want to either add them all at the same time and watch your water parameters ,or add say all the female guppies first, wait a day or two for them to settle and to make sure the water params are doing well, then add the male guppies, wait 2 or so days and check the water params, add the platies, wait and then add the girl. By adding her last, you'll know all the others are settled and know the tank well, where the hiding spots are, etc. Also, when you add her last, she'll feel like she's entering the other fish's territories, so she might be a bit more docil and calm when first introduced to them all.
oh, and pictures would be awesome