Laila Al-Matrouk of Belfast was reportedly on life support after the accident, according to a Facebook post by her sister.
Belfast Police Chief Mike McFadden says Laila was riding her bike along Route One near the Belfast-Searsport town line on Sunday afternoon when she was struck by a car.
Chief McFadden says no charges have been filed and the accident remains under investigation.
Police say the Belfast Area High School student was very widely-liked.
A statement by RSU-71 Superintendent Mary Alice McLean referred to Laila as "one of our very brightest lights."
Grief counseling will be available for students and school staff Wednesday, August 8.
That will take place at Troy Howard Middle School from 8 to 4 p.m.
There will also be a candlelight gathering on Saturday, August 11, at 7 p.m. at the gazebo in Steamboat Landing along Belfast's Harbor Walk.