She is John Wright, our general manager's secretary.
She is our general manager, John Wright's secretary.
the vice-president of marketing and accounts' secretary
RULES cited from grammar books
(1) Possessives with Appositive Forms
When a possessive noun is followed by an appositive, a word that renames or explains that noun, the apostrophe +s is added to the appositive, not to the noun. When this happens, we drop the comma that would normally follow the appositive phrase.
(2) Possessives & Compound Constructions
Generally, the apostrophe -s is simply added to the end of the compound structure: a friend of mine's car. If this sounds clumsy, use the "of" construction to avoid the apostrophe: the car of a friend of mine, etc.
(3) Possessives of Plurals
Most plural nouns already end in s. To create their possessive, simply add an apostrophe after the s.