Olga's 1st appearance was in Episode 46, where she was stalking Jock in school. Until, she wrote Jock a love letter in her introduction arc, and then they became lovers in the end. Her personality is that she is anti-social, dark, mysterious, and she is also into dark magic. She is also friends Nerd and Tiger. With Nerd being her boyfriend's best friends, and Tiger being Nerd's girlfriend. Her and Nerd didn't really get along with each other in her first appearances, but they're close friends now that she's dating his best friend Jock. Tiger on the other hand, after seeing her kissing Nerd for the first time, they had became best friends and now hangout together, and she also gives advice to her on how to talk to boys more effectively. She also wants to see more of Nerd and Tiger's relationship in progress.

I imagine her to have a more soft and quiet tone of voice that most goths talk with. Kinda of like Marceline from Adventure Time

Here's a voice reference:

https://youtu.be/3taBPm3gD10?si=ol7v1haWmVAR9pAI