One sure way to lose another woman’s friendship is to try to improve her flower arrangements.

Marcelene Cox (1900-1998) American writer, columnist, aphorist

“Ask Any Woman” column, Ladies’ Home Journal (1948-02)
    (Source)

This was a regularly revisited aphorism for Cox:

One sure way to lose another woman's friendship is to try to improve her husband.
(1955-12)

The quickest way to lose another woman's friendship is to endeavor to improve her husband, her children, or her flower arrangements.
(1959-05)

One sure way to lose another woman's friendship is to try to improve either her children or her flower arrangements.
(1961-07)