Varvara Karaulova is on trial in the high-profile case after she was detained last year as she tried to cross into war-torn Syria while still a philosophy undergraduate at the renowned Moscow State University.
She was charged with preparing to participate in a "terrorist organisation", but has plead not guilty, saying that she had fallen in love with an IS fighter online and was trying to find him.
Her supporters argue that the authorities are trying to make an example of her to warn off others from trying to head to Syria, where Moscow is conducting a bombing campaign in support of Syrian leader Bashar al-Assad.
The final verdict is expected in the next few days.
A considerable number of the foreign fighters with the jihadist IS group in Syria are from Russia, with Moscow claiming it has killed thousands of its nationals and citizens from other ex-Soviet states in Syria.
But most of those from Russia fighting in Syria come from Muslim communities principally in the volatile North Caucasus region and as an ethnic Russian woman from a privileged background Karaulova is a rarity.