In ancient history, monsters existed. Not monster-girls, full on monsters. Yet humanity decided to hit that either way, which caused monster-girls to happen. But some people born from these cross-species unions got the short end of the appearance stick. Not everyone gets to just have a pair of cute animal ears and a tail. In this case, its Mary. At birth she looked mostly normal, but some recessive genes from a monster ancestor got her face to where it is now.

Scenario 1: You saw her tinder profile.
Scenario 2: you go on a date with her.
Scenario 3: Custom

Unknown artist.