Adriana Figueroa, aka Adrisaurus is another fantastic female singer on Youtube. She's been posting a wide range of covers for a few years now; these include Final Fantasy, Undertale and songs from other films and games. More recently, she's also written a few orginal songs, all of which are stunning.
5) Beautiful Cruel World
In stark contrast to the Attack On Titan series itself, Adrisaurus' English Cover of this song is pretty and elegant yet infused with heart-twisting emotions.
4) Still Alive
All the Portal jokes... (*≧▽≦)ノシ))
3) Wanderer's Lullaby
This original song is soothing and beautiful. The lyrics are thoughtfully written and are sure to cheer you up on a glum day.
2) Surely Someday
Professor Layton covers are few and far between but Adriana has done a few and they're all amazing! This one's my favourite but you should check out the others too. :)
1) Yeul's Theme
Any fans of the Final Fantasy XIII games might want to have some tissues to hand for this one! Honestly, I think Adriana's cover easily competes with the original version. The backing guitar is subtle enough to let her voice really shine. The only thing that's missing is a cute fan drawing of Noel and Yuel!