First duel (Merula Snyde x Slytherin female reader)

The Letter

As our second and third year passed, me and Merula never found out what happened to her on the train. Our ride backs contained pretty much what happened on the ride pack from year one: Alone time, talking, and a kiss. Year four started off like any other year, and until the second month of our time at Hogwarts had we gotten a message. It said, "To (full name) and Merula Snyde". It was from Helena Orth, also known as the nurse on the train. I found the message and immediately called Merula over to read it.
"To us?" She looked at the letter. "What for?"
"I dunno. Open it!" I handed her the letter, and she started to destroy the envelope. Once she got the letter out, she took a good look at it, but didn't read it.
"Well?" I asked, excited to hear whatever the letter said. "Read it!"
"Okay, okay..." Merula began reading the letter. "'Two years ago, Ms. Snyde was somewhat "attacked." We did not know what it was, but I have a theory of what it might be. I, the nurse on the train, discovered that there just may have been a dementor inside Ms. Snyde's compartment. Ignoring the other's opinions, I feel this is the most likely cause of Ms. Snyde being pale. As she described she didn't feel happy, if you have learned, dementors suck the happiness out of you. I reckon that's what happened. Next time we meet shall be on your way back home from Hogwarts.
-Helena Orth."
I stood there, and I questioned whether it really was a dementor attack. It did seem like it were the most likely cause...
"That bloody bloke!" Merula hissed. "Took her two years to find out it was a dementor? Could've took me 5 minutes with all the evidence!"
Merula was quite angry for some reason.
"Someone's having a bad day..." I laughed.
"Besides, we don't even know it was an actual dementor."
Merula tossed the letter in the air, and I ran over to catch it.
"Fine," Merula started up. "But I still think she's an old and demented woman. Who takes two years to figure out it was a dementor?"
I stuffed the letter in my pocket. "She was probably busy, and she didn't even have to reply. You're fine anyway, aren't you?"
Merula wanted true conversation to end, that's for sure.
"Yeah, well whatever."
And like Merula wanted, the conversation ended and we started to talk about something else.

As the time between year two and three flew by, me and Merula became too close- girlfriend and girlfriend close. We never did anything about it, though. We never went out or anything like that. Our friends knew we were close, but they didn't care much and only thought we were best friends. Although... Tonks and Rowan did seem like they knew something...
I honestly just wanted to get my feelings out for Merula. I wanted to tell her that I wanted her to be my girlfriend, and I wanted to let my friends know that I liked her. It wouldn't hurt to tell them that I liked her... Maybe I could get their help and be able to finally ask her if she really liked me in that way and if she wanted to be more than friends...
It's official. Tomorrow, during breakfast, I'll tell my friends about how I feel for Merula.