Phrase(s): nuts about someone or something
Go to crazy about someone or something.
McGrawhill's American Idioms And Phrasal Verbs
Be extremely enthusiastic; also, be extremely fond of. For example, Ellen is nuts about opera, or Kevin has been nuts about Megan since he met her. This seemingly new slangy expression began life in the late 1700s as nuts on or upon; about began to be substituted about 1940.
American Heritage Idioms