Despite all of the stuff running through Adelaide's ever-busy mind, Rodeo's reaction gives her a sudden clarity. There is no way, in this life or any to come, that Adelaide can meet that hopeful question in her brother's eyes and refuse him anything at all, if she's able. It's why she couldn't go to him after his sentencing - because she never would have been able to leave, to live. She'd have been just as sentenced to death as he was.
And so she smiles at him, a real one, like the smile in that photograph that nobody recognized, because the smile isn't for just anybody. Before she accepts his hand she turns, goes on tiptoe to press a kiss to Sarge's cheek - because if she could cram them all onto that single bike she damn well would, and she doesn't care if the gesture makes the Hellhounds howl or if Sarge looks like he might evaporate on the spot.
She wants to laugh at their use of the term "Prospect", but she's too unwilling to do a single thing to take that look off of her brother's face and so instead she just hands over the keys to the SUV, takes Rodeo's hand and decides that until it's time to go, she won't think about it. "Been a while. Guess it's just like riding a bike," she jokes, because the last time she rode on a motorcycle was with him, so many years ago. With her hand in his it feels like yesterday.