Assad was married to Assef Shawkat, the former deputy chief of staff who was killed in a rebel bombing in Damascus in 2012.
"Despite the death of her husband ... the family link between Ms. al-Assad and her brother is sufficient for the council to be able to regard her as being linked to the leaders of Syria," the court ruled.
The General Court said Thursday funds she may hold in the European Union are frozen and she is prohibited from entering or traveling through any EU member state.
The court added it dismissed a challenge she filed against it for the censure.
"The council was fully entitled to presume that persons whose ties to members of the Syrian regime are established may be regarded as supporting the regime or benefiting from it and, therefore, as being associated with it," it said.
Syrian President Bashar al-Assad is suspected of committing war crimes during the civil war in Syria that began as peaceful protests in 2011.
Last week, British Foreign Secretary William Hague said it was time to refer to the situation to the International Criminal Court at The Hague, Netherlands.