Serverus Snape Fic about a OC

I read this fic 3 years ago, and I loved it but haven't been able to find it. It was a Severus Snape fic, with a OC and she was his student. She became an 'honorary' teacher, sitting at the teachers table and becoming friends with Mogonagall and Pomfrey who shipped her and Sev so hard. He taught her to do a 'rainbow lumos'.

Edit: it was on Wattpad!