Significant Positive - Meeting Fang and becoming friends at Oerba's orphanage.

Okay this is a cobbled together backstory memory. Basically Fang and Vanille's parents were all killed at the hands of Cocoon's Fal'Cie during the War of Transgression five hundred years previous to the main plot. That bit is in Zero but that is not this memory!

This one is mostly off-screen and involves Vanille meeting Fang at the orphanage after the attack and the two of them forming a close bond. Inevitably because of it, they become L'Cie together, but while that is also in Zero that is also not this memory and is rather implied so all you get is me blathering on.

It's noted that after the attack Vanille was just sad, but Fang ended up angry. There was definitely some amount of attempts to heal mutual hurts. And just looking out for each other. Fang and Vanille are very very very close. Like sisters. But also there's some degree of romantic attraction. And platonic attraction. And just oh gosh who loves Fang VANILLE LOVES FANG!1

Vanille will also remember as an aside not how her parents died but that they are dead, that something tragic happened, ie why she's at the orphanage in the first place, etc.

So basically:
+100000000 Faaaaaaaanggggggggggggggg .///.
+100 :( childhood backstory.