True, that.
Same thing - you need more commas.
Also, when did Mercedes suddenly develop 'feelings' for Gerard?
"...Even though deep down I had feelings for him, doesn’t mean I should be nice to him..."
There's a difference between finding an individual attractive and actually caring about him or her.
And watch where you do put commas. At the end of that quote, there was a comma rather than a period. Perhaps try proofreading. :) And beware run-on sentences. Those particularly tend to show up in your material.
But your content's good, so I'm not complaining too much.
By the way, you may already know, but Gerard was actually... well, not as good-looking as he is today, to be polite, back in his younger years. So that kind of messes with your accuracy, but what the heck, that's why it's fan fiction.