Which language system most likely broke down in the following scenario?

anna's cousin melinda is visiting from alabama. while anna was getting a soda from the fridge, she asked melinda, "would you like a coke®? "
"sure," melinda responded. "how 'bout a sprite®."
anna paused. "wait, do you want a coke® or a sprite®? "

phonology
morphology
syntax
semantics
pragmatics

i need and speech class is my worst suject

The language system is semantics. "Coke" v.s "Sprite." are two different words, so we are focusing on a word. When Anna paused, she was confused because to Melinda, A Coke means a Sprite in her vocabulary. She wanted to confirm the same meaning. Semantics involves a changing meaning depending on the person. She is visiting from Alabama, so the meanings may have chosen just like dialects. Thus, it cannot be phonology/morphology, syntax, or pragmatics.