Yes, Mrs. Coffield is a noun, a proper noun, the name of a person.
A proper noun is always capitalized.
Peter Coffield's birth name is Peter T. Coffield.
Darren Coffield was born in 1969.
Coffield Unit was created in 1965.
James Coffield Mitchell died in 1843.
James Coffield Mitchell was born in 1786.
Randy Coffield was born on 1953-12-12.
Glen Coffield died on 1981-06-16.
Glen Coffield was born on 1917-06-05.
Wendy Lee Coffield was a victim of the green river killer.
Peter Coffield was born on July 17, 1945, in Wilmette, Illinois, USA.
Two nouns: Mrs. Porreca, a proper noun. teacher, a common noun.
No, "Mrs. Walker" is not a proper noun. It is a title followed by a common noun, making it a common noun phrase.