I just wish the girls would not even HAVE a RES. To give you a clue as to how much they cost, you have to have 10 gallons for every inch long that they are, now imagine filters, water treatment, and care they they require. A 10 inch long RES HAS to have a 100 gallon tank. They can get stressed out and stop eating in anything smaller. Not to even mention UVB lighting, I bet if they do keep the turtle it will get shell rot and die soon after if the little sister is truely the only care for it, but seeing how the dad just sent her off with just the little carrior and turtle Id say impulse buy.
Now, there may be something better waiting at home for the little turtle, but I doubt that.
Like it was said before, basicaly the law states its illegal to sell a turtle, but not to buy one. And the law is mute because all the buyer has to say, to make it legal both ways, is that they are using it for a school project or something like that, in order to legaly sell it for Educational purposes.
All turtles carry salmonella, its not something you can get rid of, because it benifits the turtle. I think its in their Digestive track, but its more of a threat to humans than in other reptiles because they swim in their own poop. However, the reason the law states nothing under four inches is so little kids do not go around putting the little turtle in their mouths.