Protesters have remained on the Garvaghy Road since 27 September as the fallout over the proposed Portadown District Orange Lodge march continues. Rallies on both sides of the dispute were held on Saturday.
Speaking on the BBC's Sunday Politics programme, McDonald said: "There's no question with us co-operating with any process that will unfold." She added: "There are moments in political life where you have to take a stand, and this is one of those moments."
McDonald and Northern Ireland's First Minister Michelle O'Neill are among those who have attended the protest. The PSNI has said that anyone found to have broken the law will face criminal justice consequences. The Portadown District has maintained a presence at Drumcree Church after talks to end the parading dispute ended without agreement on Thursday.
When asked about the legality of the protest, McDonald said: "Others will determine whether or not that is in fact the case." The Parades Commission decided that the parade, which is opposed, should not take place as proposed.