Why did savanna ask summer wear her boyfriend was

Summer is being sarcastic and mean..... offhandedly making fun of Auggie (and Summer) at Summer's expense.

Anyway, the first thing that happened when I got to her party was that Savanna greeted me at the door and asked: “Where’s your boyfriend, Summer?”

I didn’t even know what she was talking about.

“I guess he doesn’t have to wear a mask at Halloween, right?” she added. And then I knew she was talking about August.

“He’s not my boyfriend,” I said.