Using the word really in prose, outside of dialogue, doesn't sound right, and lacks a certain professionalism.
The prose are good, until you break into conversational writing. Every now and then the voice of the narration breaks and modernizes. Not that modern narration is bad, but instead of being a narrative, the prose breaks every now and then into a word choice that seems more dialogue then actually narration. If you clean that up, you'll have a seriously sweet read.
Senna is dressed . . . inside . . . with a cloak on . . . and someone trying to be inconspicuous? Her actually goal in her dress isn't mentioned, or if it is I missed it, but for a group of secretive people like her, Dias, and Kal, wearing a veil (when no one else is metioned wearing a veil, and wearing a cloak, where no one else is wearing a cloak, is going to make people notice you. It won't hide her face, but rather paint a great big sign over her that reads something like, "Hi, I'm a suspicious person, but I'm really trying hard to hide myself in the absolute worst way possible. I'll bet the law enforcement would be interested in me."
Blending in is about just that, blending in. If every woman at the party is wearing a low cut top, and one is wearing a more modest cut, she'll stand out despite the "plainness," of the dress. More people will notice her. If everyone is covered in mud, but the same woman is wearing the party dress, she'll stand out (even if covered in mud, but less so then).
As you can see these are nit picky things. The real issue with the piece is the breaks. There are sooooooo many of them, they get annoying. And many of them seem pointless. I realize they're meant to be scene breaks within the scenes, but they just don't seem necessary. As the reader, every time I see one I'm expecting either a) a point of view shift, b) time shift, or c) an actual scene change.
Every time one of these breaks appears I feel like I'm missing something or there has been a significant passing of time. The following text gives no identification of these lapses, so I feel like there are things happening that I'm missing out on. I feel cheated.
Oh yeah, and since we've had such a connection to Rosaline, emotionally, Not having a chapter about her was kind of annoying and hard to read. Not that the stuff going on wasn't interesting, but it wasn't about her.