Lissandra’s New Lore.....Whaaa???

“The Void erupted into the mortal world in the far north, and with it, Lissandra’s hidden allegiance to the Watchers became undeniable. In that moment, her only choices were to let all the world be consumed, or to give up what she cared for most—Lissandra sacrificed her sisters and the allies they had gathered, entombing the Watchers beneath a glacial barrier of magical ice that could never be melted.”

Why? She's now written in a way that shows that she wants to stop the void. But why only these two choices? How was “Oi sis’ we need to team up an’ shit. The void is getting closer and closer so we need to curb stomp that shit outta runeterra or at least out of the Freljord lands” not an option? I had to reread this updated lore just to understand but I’m left with more questions.