User blog comment:FairyRaven/Fairy Tail Chapter 467: Mother's Key, Review and Commentary/@comment-7418318-20160107102332

I have a theory on Grammy, Layla and Brandish.

We already know that Zoldeo, despite being trusted by Layla, turned evil.

Maybe he went after Grammy to get the key in her possession. Grammy, notices something strange about Zoldeo or has a really bad premonition or something, so she sends Brandish away on some meaningless errand to make sure she'd be save.

While Brandish was away, Grammy and Zoldeo fought and thanks to Aquarius Grammy was able to drive Zoldeo away, but only after getting a lethal wound.

Layla, somehow alerted to all this, arrived too late and by the tiem she came, Grammy was already dead, so she took the key back from the dead body, clutching the key to her chest and crying, due to her feeling guilty "If I hadn't given her this key, she would still be alive" and all that.

And this is the moment when Brandish walks in on them and sees Layla kneeling beside her dead mother's body, with the key in her hands. Brandish in shock just runs away and later blames it all on Layla.

If Brandish saw Zoldeo before going on the errand, it'd make her feel that Layla's to blame even more, since Zoldeo was a "loyal and trusted" servant of Layla's.