1. Marcella was an impressionable young woman with little experience of romance. Richard just swept her off her feet when he started to date her.
2. Judy and Joe went to Hawaii on the holiday vacation of their dreams. They were swept off their feet by the warm and friendly atmosphere.

Compare to: head over heels in love. One can be swept off one’s feet by either a person (opt.1) or a place or situation (opt.2).