In a March 19 ruling, a panel of the court sided with a Houston jury that decided in 2001 that Texas oil tycoon J. Howard Marshall never intended to leave any of his $1.6 billion estate to Smith.
Marshall's will gave most of his estate to his son, E. Pierce Marshall.
David Margulies, a spokesman for the Marshall family, said Friday the family will continue to defend its case with the "same vigor and resolve it has in the past as this case hopefully nears an end."
Smith and Marshall married in 1994. He was 89 and she 26.
Smith had argued that her elderly husband had promised to leave her more than $300 million.
The case previously reached the U.S. Supreme Court, and attorneys for Smith's estate vow to again appeal to the nation's high court if necessary.
Smith died of a drug overdose in 2008 and named her 3-year-old daughter Dannielynn as heir.
The former Playboy model's ex-boyfriend Larry Birkhead and attorney Howard K. Stern were placed in charge of her estate.
Smith initially challenged the will in Houston probate court and lost.
However, a bankruptcy court in Los Angeles awarded her $474.75 million, which was later reduced to $89.5 million.
The legal dispute has centered on which court ruling to follow.