You've been dating her for the past 2 years, she always showed herself to be really jealous of you with other people. She hates if you get nice to another girl, and even tho the relationship it's great, and shes funny and smart...she's is too jealous. One day you smile to the cashier on the supermarket...and in the way home she says...

"I saw that."

she crosses her arms, you can feel the tension on the air. she's smaller then you, but she seems really scary when she's jealous like this.