Claire missed the "big bathtub," but she wanted to give a Luke surprise so she hadn't taken a soak earlier.
Now that Luke had come home, she decisively chose to enjoy life.
Luke sat next to the pool and handed them drinks every now and then. He also asked Claire about her itinerary for this trip.
Claire was about to be an adult now and would be going to college, so naturally, Luke shouldn't arrange everything for her.
Claire also wasn't someone who couldn't take care of herself. She was very independent. Luke wouldn't help arrange everything for her; letting her handle things herself would be the best option.
Claire then nattered on.
In short, there were two points. Firstly, she would stay in the college dorm in her first academic year to better adapt to college life.
Secondly, she would go out on her own in a couple of days to check out the study and living environment.
In other words, Luke and Selina weren't part of her plan.