That's MY spoon!

There's been some interesting communication going on between the two kids. I'll give you a few examples:

Scene One
Marian: Baba gaga mmmm lala mmmm (plus other baby babble noises- you get the picture)
Ella: NO! MINE!
Marian: AHHHHH!
Ella: MINE!
Marian: EEEEEHHHH!
Me: What are you two fighting about?!
Ella: Marian says she wants my spoon but I say it's MY spoon, Marian!
Me: Why don't you get your sister her own spoon then?

Somehow giving Marian a spoon did solve their bickering. Although Marian does love spoons and simply may have been distracted from whatever she actually wanted by a shiny object.

Scene Two
Marian: Again, happily babbling away. Crawls over to the dog bed which is a big no-no in our house. 
Me: Uh-oh Marian! No dog bed!
Ella: Mama, don't say, "Ought ought ought" to Marian. She just pretending to be a dog.

Seriously, what do you even say to that kind of stuff? I went with, "Well then she can pretend to be a dog somewhere besides the dog bed." Ella told Marian to come be a dog next to her and they crawled around doing some game of their own making.

So here's my question- how much of this is my toddler making stuff up vs. the two kids having their own little mode of communication? I noticed a long while back that Marian doesn't talk as much when Ella is around. Whether that's because the poor kid can't get a word in edgewise or because she is relying on Ella to communicate for her is up for debate. Parenting experts, what say you?