Once the immediate threat of Gabriel being overtaken by plants was taken care of, Nero had a decision to make. The way he saw it, he could barricade his room and wait here till help came. That would most likely be the safest and most logical option. After all, he was a student, not a teacher. His priority should be to take care of himself and survive the sudden crisis, not try to face it.
Although the window in their room could only open partially, and the jump from the first floor to the ground floor was not exactly small, it still served as a decent escape option in case of an emergency.
But the most logical option was not necessarily the best option. Nero looked down at Gabriel, still laying on the floor, completely disoriented. Killing the vine had been especially taxing on him. Who knew what measures the vine had taken to try to protect itself? Excruciating pain would only be a part of what he felt.