легкомысленный Englisch:

I think he sees her as a frivolous young woman

The politician's frivolous (thoughtless) behaviour was criticised and his popularity fell out.

frivolous ribbons and lacy frills / the frivolous, fun-loving flappers of the twenties

Definition: lacking in seriousness or importance Antonym: serious, sober Sentence: Kim Kardashian’s frivolous marriage annoyed me because I don’t think either of them were ever serious about their relationship.