Maybe dare doesn't betray her squad, we know during the daytime sequences you play as all the squad except the rookie, maybe you DONT play as one of the squad members, and maybe that squad member is a traitor, say dutch for example, first, you play as everyone ELSE during the daytime sequences, maybe even dare, but not him, and then at the end of the night sequences, you see him ready to detonate a building full of the ODSTs saying to himself something about now that he has all of them in one place and has fooled them into thinking that is a pickup point, he can detonate the building, and help the covenants cause.
Or see him with a pistol to one of the squads head, and hear him talk about killing him like he did the other, then he sees the rookie, wounds the last remaining squad member and fights the rookie, what do you think?