It can also have reverse effect, like for me, where I hate her even more now.
You don't do that to someone you've known since childhood, someone who truly loves/loved you.
It's playing with persons heart for your own gain.
She could have taken a way out, it's obvious they had relationship problems (shocking!), broken relationship and continued watching from distance, but nope, seducing and manipulating is easier. She's definitely 100% Templar material.
Small edit: You should probably use fast forward through seen text of chapter 1 to see the scene immediately before "do you still love her". It's very short, but does good job of showing them grow up together.