Good that you re-installed The Sims 2. 🙂 I still can't get used to how Sims look in The Sims 3, they're too cartoony/ clay looking with lack of texture detail.
My Sims 2 version of Sachi looks cute and she's slender like Regan is supposed to be. You can't make Sims 3 kids slender/thin at all because they have fat necks and are naturally chubby.
See? This is my Sim of Sachi/Regan in TS3. She's chubby, has a fat neck, and I try to hide it with the hair in front of her shoulders.

I can never make her look like my Sims 2 Sachi/Regan:
