The 29-year-old actress took photos with fans on her way out of the building.
Sienna was offered £100,000 from UK tabloid News of the World after the publication admitted to eavesdropping on her voicemails back in 2008.
However, if she doesn’t accept the settlement, called a Part 36 offer, Sienna will have her case thrown out and would have to ask for less than the original offer, The Independent explains.