It's Punky Brewster

Punky the Heiress (2x4)

Air date: Sep 20, 1986

Punky's aunt Rose and uncle Roy invite her to the Chester Henderson mansion under the pretense that they have found her mother. What Punky doesn't know (until Glomer tells her) is that she is dressed like Henderson's granddaughter Debra so Rose and Roy can use her to embezzle Debra's $50 million inheritance.