Sera usually spends her bigger blocks of free time back at home on the berry farm her family owns :] she likes going and helping out with anything she can (and also annoying her younger siblings). Most of the time that just means that she's performing routine check ups on the helper Pokemon there, and then goes back home with lots and lots of fresh berries! Yummers. Shorter bouts of free time are spent with friends or on her own, doing independent research. Such a busybody...
On the topic of the berry farm, it was actually helping out there as she was growing up that sparked the initial interest in becoming a nurse! Sera used to come across a fair bit of injured Pokemon that wandered onto the farm in search of food, and would nurse them back to health (she got most of her team this way, actually)! On top of that, she grew up as the oldest of 5 children to fairly young parents, so she kinda put it upon herself to take really good care of them and their health whenever her parents couldn't, and even when they could. Nursing was just something that came naturally to her, and it seemed obvious that it would be a big part of her future, too. :)