Under the laws of heraldry, women, other than monarchs, do not normally bear helms nor crests; instead, the coronet alone is used (if she is a peeress or princess).
Married women, however, always display their arms on a shield (except peeresses in their own right, who use the lozenge for their peerage arms even during marriage).
A peer derives his precedence from his highest-ranking title; peeresses derive their precedence in their same way, whether they hold their highest-ranking title in their own right or by marriage.
