Since the beginning i have thought this to be a case of jealousy (for unknown reasons) and a female perp. Jmo ... but here are some interesting arson facts from
http://www.drtomoconnor.com/4050/4050lect04a.htm
The SIX MAIN TYPES ACCORDING TO THE FBI CLASSIFICATION MANUAL:
ARSON FOR REVENGE (41%) - precipitating factor is a real or imagined affront that occured months or years ago; attack is focused on individual rivals, a business chain, schools, or some facilities connected with offender
ARSON FOR EXCITEMENT (30%) - precipitating factor is boredom, (sexual) thrill cycle, or need for attention; attack is focused on large or outdoor targets, like parks, construction sites, arenas, as well as residential areas
ARSON FOR VANDALISM (7%) - precipitating factor is family disturbance or peer pressure; attack if usually focused on educational facility as well as residences and outdoors
ARSON FOR PROFIT (5%) - precipitating factor is a recent financial loss which triggers an urge to cheat the insurance company, recoup a bad investment, or dispose of some depreciated assets
ARSON FOR CRIME CONCEALMENT (10%) - precipitating factor is a desire to cover up some other criminal activity, such as auto theft or murder
ARSON FOR EXTREMISM (7%) - precipitating factor is to further a social, political, or religious cause, or to burn down buildings associated with specific races or religions
Adult arson is usually a product of vanity or egocentricity (Orr 1989). When the perpetrator is male, the motivation is more cold-blooded or instrumental; and when the perpetrator is female, the motivation is more hot-blooded, emotional, or affective (Gannon 2010). Professor James Ogloff, director of the Centre for Forensic Science at Monash University in Australia, says the profile of a typical fire setter is male, late teens/early 20s, unattractive, unmarried, shy, socially isolated, and with lower intelligence. About a third of perpetrators have co-morbid psychiatric conditions including schizophrenia, and mood and/or personality disorders (usually narcissism). About half have prior criminal convictions. One of the more curious clinical characteristics is the apparent lack of motive (typically reserved for the so-called pyromaniac). No arsonist shows remorse, but only the pyromaniac lacks conscious motivation although they are fully aware of the acts they are committing. It's as if their mind "blocks off" or conceals short-term memory of whatever rational thought they put into their devious plans. For this reason, clinicians often characterize the motivation as a combination of pathological and non-pathological.