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)