Should I have taken advantage of my orientation-questioning friend?
How were you able to take advantage of her?
She had so many problems with human relationships, so she never got the chance to be successful
It's not ethical or moral to use someone else to gain something for your own benefit. Talk to your friend and communicate so you can try to make amends.
I can't just tell her how I took advantage of her and make her my enemy.
It would be better to confess your wrong doing than trying to ignore it. Try apologizing for how you treated them and ask for their forgiveness. You can't undo what you did, but you can learn from it and be a better friend to her.