"I can sit all in the back," Milo mumbled softly.
"Don't be silly," Sloan said, moving to the last row of seats, "If you're being dropped off first, you should get the middle, because that way it's easier for you to get out. What's more uncomfortable? Sitting in the middle or having to awkwardly climb over the person in the middle row?" Milo had to agree he couldn't argue with that, so he sat in the middle row, texting his grandparents that he was on his way back, and sat hunched looking out the window, trying to matter as little as possible, whereas Sloan chatted happily with everyone the rest of the trip.
When Milo got out, he mumbled thank you to Xander, goodbyes to everyone, and quickly said, "It was a fun party, goodbye now, be safe." before hurrying back inside. After he was gone, Sloan nearly made a (well-meaning) comment about Milo's behaviours, but decided against it. Although she knew she wouldn't mean anything negative by it, she didn't want to accidentally come across the wrong way.
Once back at Becky's house, she got out, and much more profusely thanked Xander and Alec again, and when they walked up Becky's steps, asked, "Did your parents know about this the whole time?"