To sweep someone off their feet

To have someone fall in love with you quickly because you are exciting or attractive.

e.g. my cousin met a man a few weeks ago. He takes her to lovely restaurants, he’s really charming and he’s always buying her flowers. He has really swept her off her feet.

ps. Similar to that is to fall head over heels (in love).
It means completely, suddenly deeply.
The term smitten with someone is like it e.g. my sister is smitten with her new boyfriend.