Ms Long said they highlighted a rising dissident threat from dissident republicans.
On Sunday, police foiled a plot to fire four mortar bombs at Londonderry's Strand Road police station.
Two men have been charged in connection with the planned attack, which has been linked to dissident republican activity.
She said that they did not request additional resources to deal with the security situation, but had made their concerns known to Mr Cameron.
Months after protestors took to the streets following a Belfast City Council change in flying the Union flag, the continued unrest was also on the agenda.
The East Belfast MP said they also discussed wider implications of the recent developments in terms of loyalist violence and "deteriorating political relationships".
Speaking to UTV, she condemned recent criticism from politicians over the PSNI's handling of flag demonstrations.
The First Minister Peter Robinson claimed on Monday that there is a "perceived unfairness" in how loyalist protestors are being treated.
"I think in a week when police have foiled such a significant dissident threat, when they have really been holding the line between rule of law and mob rule, it was a deeply and profoundly unhelpful comment to make," she said.
"I believe it is incumbent on ministers in the Executive, in particular the First and deputy First Ministers to lead Northern Ireland in a way that is line with the conditions that they placed upon themselves in the St Andrew's Agreement.
"They should support the rule of law and the PSNI, they should do that in an unequivocal way and in a way that builds confidence in the community, and I don't believe that in simply echoing complaint from certain sections of the community was necessarily building that confidence."
The Alliance representatives also discussed events taking place in the region this year which will put a spotlight on NI, including the City of Culture, World Police and Fire Games and the G8 summit.
The MP added: "There are huge opportunities this year to showcase the positives of Northern Ireland on an international stage, but they also each provide security and policing challenges, particularly in the current context."