The teen was at the hospital waiting to be seen on Dec. 4 and was given a book by security to keep occupied.
Police allege the 17-year-old used the book to strike the overhead sprinkler system which caused it to spray out water for 40 minutes before staff were able to turn it off.
The hospital said the flooding caused significant damage, with 20 per cent of the department being taken out of service for three weeks.
Affected areas included four treatment rooms, five seated patient areas and two hallway spaces.
On Thursday, police announced the teenager was arrested on Tuesday and has been charged with mischief over $5,000.
She will appear in court on Feb. 23.