Bagels.

Beth was hungry, and despite the fact that she was trying to avoid a lot of carbs so she could fit a wedding dress, she couldn't turn down the invitation.
"Sure."
"Excellent! We'll walk. That way you don't have to feel too guilty about the carbs, okay?" Derek laughed and childishly grabbed at her love handle, pinching some of her body fat.
"Stop that!" Beth slapped his hand. "Jerk..." but there was no anger in her voice. Derek still acted superficially like a frat boy sometimes, but it was always playful and good-natured. At least, that's always how Beth reacted to it. Whenever Brian was the target of Derek's jokes, Brian never seemed to have a sense of humor about it.
They walked the half mile to Bagels4U! It was a tiny, simple place that smelled of yeast and coffee. They sold bagels, sandwiches, coffee and smoothies. Derek ordered a sesame bagel with strawberry cream cheese and a coffee. Beth splurged on a bacon egg and cheese sandwich on a whole wheat bagel with a strawberry banana smoothie made with fat-free fro-yo. They sat in the corner, listening to top 40 and chatting. There were at least four other customers clearly from the gym, and she even recognized a few and nodded hello. She wondered why they all seemed to be looking at the two of them with little smug smiles. Maybe it was Derek's reputation as a skirt-chaser around the gym. Beth didn't pay much attention to gossip, but if the snippets she heard were to be believed, Derek had his share of gym bunny conquests over the years.
"So, Brian's really dead set against me, huh?"
"Derek, I told you, he's got nothing to do with it."
"You don't have to lie to me. It's fine. He's obviously still a baby." Derek didn't seem annoyed. "Besides... I don't need an invitation."
"You... can't crash my wedding, Derek." Beth flicked a sesame seed at him.
"Oh, I won't be..." Derek grinned.
"Then what...?" she stopped when Derek held up his phone, showing a text exchange. It was between him and Lindsay. They knew each other through mutual friends in the entertainment industry, and Lindsay never failed to talk him up around her. The text messages told the story: Lindsay had asked Derek to be her plus one.
"What?!" Heads whipped towards them, and Beth lowered her voice, red-faced.
"Well, when I told her I never got an invite..." Derek smiled like a misbehaving kid who got away with something.
"You... she can't.... Brian..." Beth bit her tongue. Oops.
"Just as I thought." Derek nodded, having his suspicions confirmed.
"Derek..."
"It's okay, Beth. I knew the truth. You're a sweet girl for trying to cover for him. You're going to make someone a good wife someday." He smiled. She couldn't help but notice he had said "someone," not "Brian."