Lisa was distinctly unnerved by Sassy's existence (and name; she muttered something, at some point, about Homeward Bound). She was even more unnerved by the bear's cooing, and she didn't really bother to hide it because this is a creepy bear ok.
But she played along and made a sort of wish, though it was more that Mandy was okay wherever she was than anything at all related to the school year. Expelliarmus is a relatively sane spell, so she wasn't too worried about her wand performing and managed the spell with ease. After that, she went over most of the charms she'd learned since first year, though she tried to avoid anything that would make her bear get too excited because creepy bears.