You can do a lot of things from the Edit Town function. You can find it on the main menu when you're actually in-game. You can bulldoze existing empty houses, build new ones on empty lots, place pre-made houses and families that you download from The Exchange on the official Sims 3 site. You can also merge and split any family that lives in the town. I'm not sure exactly how you would put the duplicate of your Sim into your family, but if it can be done, Edit Town is the tool for it. It's also where you can switch to a different family within the same saved game. The things to remember when doing this are that you will lose all the promised wishes in your first family when you switch to another family. You will also lose anything stored in your refrigerator. And, your family will continue without you unless you turn off Story Progression. You could come back to find that someone in your family got married and moved out! Or had a baby!
I hope this helps. If you have any other questions, please let us know.
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Edit: There's also another option that may restore your deceased Sim. The games keeps a copy of your previous save, so you might be able to restore it to a point before she was so far along in starvation. Here's the link to the forum post that give you the instructions:
http://www.carls-sims-3-guide.com/forum/index.php?topic=6.0
