flighty

1. ADJ If you say that someone is flighty, you disapprove of them because they are not very serious or reliable and keep changing from one activity, idea, or partner to another. 反反複複的[表不滿]

Isabelle was a frivolous little fool, vain and flighty. 伊莎貝爾曾是一個輕率的小傻瓜，自負而輕浮。