A 26-year-old woman with dual American and Israeli citizenship who has been jailed in Russia since April after authorities allegedly found nine grams of cannabis in her luggage, has been sentenced to seven and a half years in prison, her sister said.

Naama Issachar's sister, Liad Gold, told Fox News on Sunday that her sister was sentenced Friday and the family has reached out to Israeli Prime Minister Benjamin Netanyahu for her. She said the prime minister called their mother the day of the sentencing to let her know that he will do everything he can to have her released as soon as possible.

“I feel incredibly terrible and sad and heartbroken for her,” Gold told Fox News. “She is very strong but she won’t survive there much longer.”

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Issachar, who was born and raised in Fair Lawn, N.J., and moved to Israel when she was 16, was returning home April 9 after a three-month trip to India, Gold said. Issachar, who has served in the Israeli army, was stopped by police at the Moscow airport as she boarded her connecting flight to Tel Aviv, brought into an interrogation room and was told cannabis had been found in her checked bag.

Issachar said she accidentally left the cannabis in her bag, her sister said. The 26-year-old was initially charged with cannabis possession, but the charge was upgraded in May to smuggling drugs into Russia.

Gold told Fox News her mother, Yaffa Issachar, who lives in Israel, has been in Russia for the past six months and plans to be there until her sister gets released.

She said her mother spoke with her sister, who was “shocked and scared” when she learned her fate, “but she knows we are doing everything we can to get her out.”

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Tapes of Issachar's hearings were released on Saturday night on Channel 12 in Israel, which show the 26-year-old telling the Russian judge, "I am aware that I acted irresponsibly before my flight, that I should have been aware of all of the items I have on my person. That is the reason that I took full responsibility for Charge 228 (possession) in my first trial in April," The Jerusalem Post reported.

Gold told Fox News her sister denied charge 229, which is the smuggling charge.

Netanyahu's office said the prime minister "personally intervened on behalf of Naama Issachar in recent weeks," according to The Jerusalem Post.

Netanyahu reportedly spoke with Russian President Vladimir Putin about Issachar's case when he visited Sochi last month and brought the topic up again during a telephone conversation this week.

“I think the punishment doesn’t fit the crime. I think it’s extreme and inhumane and she’s more than paid the price for what she did,” Gold told Fox News reacting to her sister’s sentencing.

“We continue to urge the Israeli government and the prime minister to continue to be involved in her case because she is being treated unjustly and unfairly in our opinion.”

Gold said she is “very happy and very grateful” that Netanyahu is involved and taking “a deep interest in my sister.” She added that she is optimistic they will find a way for her to get out of prison.

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“We will never stop until she’s out,” Gold said.