Buyuksarac, who was crowned Miss Turkey in 2006, was briefly detained last year, a year after she shared the poem on Instagram. It apparently used verses from the Turkish national anthem to criticise Erdogan.
She later deleted the post, which was originally shared in 2014, apparently on advice from a friend who had warned she may have committed a crime.
Buyuksarac, a graduate who describes herself as a designer and writer and has worked as a model and appeared on a reality television show, was one of thousands of people to share the poem.
It did not mention Erdogan - who was then Prime Minister - by name, but alluded to a corruption scandal that allegedly involved his family.
It was titled The Master's Poem, an apparent reference to Erdogan's remark that his third term as Prime Minister would be his "master phase".
The President's lawyer told the court that Buyuksarac's actions had gone beyond "the limits of criticism" and amounted to "an attack" on the President's personal rights.
In public comments last year, she pointed out that she had not been responsible for the adaptation. "I shared it because it was funny to me. I did not intend to insult Recep Tayyip Erdogan," she said.
Turkey's new wave of defamation cases are part of a growing tightening up of enforcement. The trials have prompted alarm at the erosion of rights and freedoms in a country once seen as a model of Muslim democracy.
Erdogan's Government has also been criticised over its decision to pursue cases beyond Turkey's borders. In April, Turkish lawyers invoked a rarely-use German law to file a case against a comedian there, Jan Boehmermann, who had performed a poem insulting Erdogan.
When a German media executive jumped to Boehmermann's defence, the lawyers tried - unsuccessfully - to bring an injunction against him too.
The controversies come almost two decades after Erdogan himself was jailed over a poem he read at an Islamist rally. The Turkish leader served four months in prison in 1998, after prosecutors said it challenged the nation's secular order. Erdogan has said the poem was "was an attention-getter".
Turkish authorities insist that personal freedoms in Turkey have increased under the rule of Erdogan's Islamist AK Party.
Turkish police detained more than a dozen activists and imposed a heavy security blanket in Istanbul on the third anniversary of protests that posed the biggest challenge to the President's rule.
The 2013 protests began as a grassroots movement to stop plans for the redevelopment of Gezi Park in central Istanbul but snowballed into a wave of nationwide wave of anger against the authorities.
