Wasn't Napoleon actually average height back in the day?
Shh... don't try to disprove TV Tropes.
Even if you may be right...<Snipped quote by KoL>
Hm.
Well. There are other ways of being bigger. What Eris lacks in height she makes up for in other ways.
And Cassandra doesn't really see herself as taller
That's cute... Actually, Eris likes her size, it's just that next to Cassandra she feels that she should be a bit, hmm... bigger. Not in the size, properly said. Eris feels kind of awed by Cassandra and so she which she could be on the same footing as her, it's not envy as well, just that feeling one gets when they are before someone that they feel that are really worth of their admiration.
However, since Eris is a bit too blunt to understand that, she turned only to the size difference part of it.