Kids left the house? Friends all dead? Too poor for a simbot? Then run on down to the consignment store dumpster, grab an old mannequin, and toss some of your clothes on it.
Sarah is based on a Mirror and as a result can be used to practice speech, gussy up, check yourself out, or change your appearance.
There are two minor issues:
Her icon looks like a grey blob.
Her shadow is off. But this is only an issue if you place her outside.
Costs 350 simoleons and found under Mirrors. Requires Ambitions.