I'm Really Hoping She's More Of A Nerd Though To Round Out The School Trope Trifecta - Tumblr Posts

I really like this theory for Marcy's whereabouts too.

Plus I really wanna see more salamanders they’re my favorite irl amphibian.

Quick Amphibia theory: 

Anne is with the frogs in Wartwood.

Sasha is with the toads from Toad Tower.

So that begs the question, Where did Marcy go after they got transported to Amphibia?

Well, I think she may have ended up in a area with a large salamander/newt population. Salamanders and Newts are amphibians and we have seen other creatures besides frogs in Wartwood such as Leopold Loggie ( an axolotl) and Albus Duckweed ( a newt ).

As for what the Newt-Salamander society is like I assume that they are the aristocratic type whom unlike the Frogs and Toads do not partake in frivolous violence. (I’m mostly basing this off of Albus’ personality and wardrobe but there’s no guarantee all of the newts have the same mannerisms as him). 

We don’t know what Marcy’s personality type is yet but if she does end up in an aristocratic society of newts and salamanders, I think she might be a bit of a jock. It’s be interesting to see a jock type character trying to fit in with a bunch of snooty well-off people while trying to find a way home.