Here is what was advised for me for my Musk turtle and it is pretty much the same for the RES. First and most important she will need a suitable place to lay her eggs, they are picky. You have to give her enough soil to bury her eggs in and this usually means 10 inches or so from what I am told. Then after she lays them you have a couple of options. You can leave them burried just as she laid them if it is in a removable container, then just keep it at room temp. say in a closet or something away from drafts and A/C. Or you can incubate them at about 82*, I am not possitive on the temps but I believe that is about mid range so you will end up with some males and females, if you go higher you will get females and lower will be males. Be sure you never turn the eggs, they MUST stay just as she layed them. If they are turned it will kill the baby inside, they are not like bird eggs that need to be turned to develope right. If I have advised wrong someone please correct me, this is how I done my muskie and it all worked good except for my own mistake of dumping the dirt when I thought she had not layed the eggs. She was sneaky and laid them with out me noticing, I should have just left every thing alone and I might be having a baby musk turtle about now. Oh well .. lesson learned I guess. Good luck, though I suspect from what you said of her size it will still be a nother year or so before she actually lays you some eggs.
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Slow and Steady wins the race...