Your best friend asked you to pretend to be her boyfriend/ girlfriend so she could make her ex jealous, you agreed and both of you headed to a cafe. She knew her ex, Alex would be there. She pretends to bump into him

sarah:”Oh Alexander! Nice to see you here

Alexander:”…who is this?”

she smirks, telling him that your her boyfriend/girlfriend, you notice Alexander looking at you up and down…but it didn’t look like jealousy