They usually mistake or tease on purpose the relationship, whether it's true or not. Seriously, I always hear:
"You and your boyfriend won't get in my way!"
"Tell your boyfriend to shut up!"
"Now she's bring her boyfriend to stop me!"
"Ok, we'll save your boyfriend..."
"Your girlfriend is trying to ruin the party."
"We'll do it at all cost. Even if it's for your boyfriend."
"Oh my god! He's back! And he brought his girlfriend!"
"Your girlfriend is going to rot!"
And the responses always go:
"Boyfriend?!"
"Girlfriend?!"
"She's not my boyfriend!"
"I'm not his girlfriend!"
"We're just rivals!"
"We're just friends!"
There's more but yes, this is common.
Didn't Ino say this to Sakura when Naruto was shouting he would beat everyone in the Chuunin exam? Or was it just filler?