The theory of Life Patterns was something Lin Yun had not yet encountered; it is knowledge reserved for those in the Enlightened Realm, and typically, masters do not discuss such matters with their disciples.
One must comprehend it all on their own; otherwise, being told what kind of Life Pattern you have can make one feel like a puppet on strings.
However, those who have reached the Enlightened Realm know that indeed, people are puppets under the control of fate, which is why cultivators strive to change their destiny.
This does not include those with special life-grids.
Such individuals are generally born with a mission; simply put, while the destiny of others is thrown carelessly, landing wherever it may, the special life-grids are arranged very clearly.
Lin Yun knew that Lin Yu possessed the White Tiger Destiny.
Her fate was to have all those close to her die in accidents, in other words, to be "killed" by her.