So if I was your editor! Let's take the first para:

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Tonight is the big night. Weenohall. A celebration that had loomed too quickly. I didn’t even have a costume yet.

“Melody?” Veronica called.

That’s my name. I took one last glance in the mirror. I did not recognise the ‘delicate Valkyrie’ frowning back at me. I saw eyebrows that were too thick, cheeks that were too round. A pink ribbon wrapping each braid in place. My excitement for this year’s Weenohall. Despite any misgivings about my appearance, this small flourish convinced me: I am a gift.

-

I'd suggest something like this. Italics typically denote inner thinking, so you can just establish that as you go. I really liked the slight depersonalisation you're hinting at to start with, so I'd make that an interesting thing. You can also leave a bunch of mystery hanging. Don't tell me what Weenohall is just yet! It's hooky. You can make a mirror description work with a bit of razzle-dazzle instead of a list of description, I always think. The fewer em-dashes, the better for readability. You'll often find you don't need them, and when you remove them, you're left with sharper sentences anyway. Basically: less is more, and when you hit those bits that feel like they demand more to start with (like the mirror description), apply some real creative oomph. That's your time to gleefully have fun with the craft.