"The Shadow Isles. They say they don't exist ... "
 

Uh ... what? When has anyone ever suggested that the Shadow Isles aren't real?

The Twisted Treeline has been based there for a little shy of 20 years in-canon and several members of the League hail from the Isles. What reason is there for people to believe they're a myth when both of these things are common knowledge?

The same way the Void doesn't exist, despite havin' proof. People probably doubted that it was as it was, being full of undead ghosties.

Maybe when Elise first visited the Shadow Isles, they were mythical.

Exactly. While the summoners and League champions might know the truth, the population at large probably don't really believe that such a place exists (just rumors and the stuff of ghost stories).

They say they don't exist? What are you talking about, Elise? It's right on the map!

It's actually not that far from Demacia.It's not much farther than the distance Ionia is from Noxus.

Who knows when she came, she could of been 10 and her partner was her father. Who knows.
Edit- And I forget to take out how she has delayed her mortality, she could thousands of years old, during the rune war period even/

Twisted Treeline was JUST moved to the Shadow Isles, it didn't exist there before.

If it didn't exist before then why was it on the map? Someone had bound to be there to get the shape of the area accurate enough to put on a map.

What Demonik187 is stating is that TT use to be somewhere else, straight from the TT Lore "The arena itself is located north of the Ironspike Mountains in a large expanse of forest nestled between the city-state of Zaun and one of the major passes that connect Noxus with the northern reaches of Valoran." Now it is located on Shadow Isles.

Spiders suck at geography.