She may have initially felt shocked when she realized her shoes were gone. After all, it's not every day that you lose your shoes while on a ride. Then, as the reality set in, she might have started to worry about how she was going to get her shoes back or what she was going to do without them. If the rollercoaster area was crowded, she might also be a bit stressed about having to search for her shoes among all the people and chaos.
She could be frustrated as well. Losing her shoes means she has to find them or walk around without them, which is inconvenient. Also, if she was with friends or family, she might feel a bit self - conscious about the whole situation. Imagine everyone else has their shoes on and she's the odd one out. It would make her feel a bit out of place. Moreover, if the shoes were new or special to her, she might be sad about losing them on the rollercoaster.