Revenge on a Salvatore

What happened?

The second I step in the door of the Salvatore Mansion Damon's bourbon glass comes flying at my head, I grab it.
"Now that's no way to welcome your baby sister is it?" I tease throwing the glass at his neck, of course he dodges it.
"It wasn't a welcome" he says rolling his eyes.
He pinned me to the wall, "What are you doing here?" He says through gritted teeth.
"That's for me to know, and for you, to dot dot dot." I smile and snap his neck. I step over him as Stefan walks in the door.
Stefan looks worried, "Grace, are you okay, what happened for you to flip the switch?"
I laugh "what happened?" I repeat back to him "what happened was my brothers killed my father, my best friend, turned me into a vampire, then I fell in love so i turned it back on, but then a witch bitch stole him with a spell" I pause "what happened?" I ask rhetorically.
"Who did you love?" Stefan asks, I can tell he genuinely cares.
"None of your business" I say casually "what matters right at this moment is you chose a girlfriend who is the doppelgänger of Katherine Pierce."
"Doppelgänger? What do you mean?" Stefan asks stepping forward.
I roll my eyes.
"Why do you think they look identical? A  coincidence? " I say stepping to him "the doppelgängers curse."
"What is that?" Stefan asks getting closer to me.
"Now, if I told you, that will allow you to kill me, so I will just hold onto that information for now."
Damon groans and gets up, "what were you talking about?"
"Grace knows why Elena looks exactly like Katherine" Stefan says.
"Grace you have five seconds to explain!" Damon shouts standing inches away from me.
"Why do you care about Stefan's girlfriend?" I sneer. That's when I see the look the two exchange.
"Wait a second," I smile "you love her too? Like Katherine? History does repeat itself."
Damon puts his hand through my chest to my heart, I grunt.
"Don't you dare compare Elena to Katherine EVER! Now, you tell us why they look alike or I will end you right now!"
I cannot stop myself from laughing, "you should be even more concerned knowing that it will put Elena in danger and most likely kill her. You can't kill me, who will tell you about the dangers or how to protect yourselves?" I ask, that makes Damon let me go.
"You will stay here, and not leave my sight, I don't know what you know or what you want or are going to do but I will do whatever it takes to keep Elena safe, including killing, using or torturing you. You understand?" Damon threatened.
I smile sweetly "whatever you say, don't worry, I'm more mad at Stefan than you, after all he did kill Father and Elizabeth then turn us" no matter what Damon says, I know he will never kill me, and I know Stefan will protect me if Damon gets too angry. 
"I'm gonna go to my room" I say as I walk up the stairs.