User blog comment:IamJakuhoRaikoben/Chapter 468: Memory of the Stars, Review./@comment-24546844-20160109233400/@comment-5266348-20160110083240

"What I don't get is how does this story go from "Mother never came back from her visit" to "Layla killed my mother because of the key"."

That's easy. Grammi leaves to visit Layla. She never returns. Instead Brandish receives news that her mother was murdered while visiting the Heartfilia property. There are no witnesses, and no suspects. Brandish later learns that Layla's daughter now has the cherished key that was last seen in her mother's possession. If you're Brandish do you conclude:

1. Grammi cheerfully gave the key to Layla or Layla's daughter and was coincidentally randomly murdered while leaving the property.

or

2. Layla wanted the key back to give to her daughter, Grammi refused to give up the key she cherished and started to leave, so Layla had someone murder her for the key before she could get too far.

Number 2 is a much better fit for the evidence previously available to Brandish.