Hana Gul Khan, 22 of Meyrick Road, north-west London, was convicted of sending the money to Jafar Turay, 28.
Mr Turay left the UK in July 2012 to join rebels fighting President Assad's regime.
He first travelled to Saudi Arabia and Egypt before crossing the border into Syria from Turkey in June 2013.
Mr Turay was previously known as Joel Kelvin Daley before he converted to Islam and was wanted by police in connection with a serious assault before he fled the UK.
During the trial the jury heard that Khan and Mr Turay kept in touch via the WhatsApp message service.
Khan raised some of the cash she arranged to be transferred by selling the contents of his flat, the court heard.
The jury was also told Mr Turay sent pictures of children posing with weapons and of him posing with an AK-47 and heavy machine guns.
In response, Khan told Mr Turay: "You look beautiful", the court heard.
Anton Atkins, 30, of Woolwich Common, south-east London, who was also accused of helping Mr Turay, was cleared of all charges.
Khan will be sentenced on 27 March.
The girlfriend of a British man fighting in Syria has been found guilty of terrorism offences after she supplied him with £1,000 in cash.