The style in which you've written this is great - short sentences which clearly show Marnie's mood and the stream of consciousness style is similar to the way all the main characters of the show talk. You could almost imagine Marnie saying this directly to Hannah in some instances.

I also like the way you have used facts from the show, directly relating back to Hannah's greasy forehead for example is the type of thing that would come up in an argument between Marnie and Hannah because it is so trivial.

The only thing I would critique is that some phrases are cliched,for example, "Deal with it, world!". I can't imagine the character saying that in the show as it edges a little to close to cheese and Girls is far from cheesy!

I like it, really sounded like Marnie.

I like this story I tried writing one, then it finally hit me I can't get into their heads. You did this wonderfully! Although one thing spell check you didn't spell 'Hanna's' name right. Other than that this is beautiful.