Other opinions based on observations by Amy of Yandere^2 Blog.
Based on an article wrote by Amy on their blog, She stated that the three main apparent reasons why a yandere snaps is because of:
TYPE A: Entering a love triangle/other polygon, hating the competitors to the point of trying to kill them.
Type C: Self-harm in hopes of getting attention from the target (e.g. suicide by falling from a building to separate a couple like Kotonoha, cutting her own abdomen up etc.),
Type B: Too much love, taking everything from the target in order to keep him to herself (e.g. locking him in her room).
Well with this as basis I fairly concluded that all are accurate and well based on the definitions of being a Yandere. Might as well add, Yanderes snap because of the with holding pressure within them that are due to too much love and their loved ones reacting differently from what they perceived or want or imagined this people would be. Honestly this are defensive mechanisms because of being selfishly and wanting selfishly the attention of those people and failed on acquiring them in the same intensity, neither less or more. Therefore, having others judge us yanderes as psychotic, obsessive and other synonymous words.