Please hit me up on PM if you would like to chat about possible relationships with my character. She is a little older at 26. 

Potential ideas: 
1) Might have been in the same year as older siblings in high school.
2) Maybe used to be your babysitter when she was a teenager.
3) Potential rivals from high school. She was bullied by fellow students. 
4) Maybe you knew of her in high school but never tried to befriend. Second chance at it now. 
5) Rival witch families. Her parents are warlocks not witches. I could see more powerful legacy families looking down on her family because they were weaker and her being resentful for it. Maybe this carried over into how she was treated in high school and now?