The 1617 reference is to a marriage contract. There is no indication as to when the marriage will take place. Mary Campbell is described as the youngest lawful daughter of Archibald, Earl of Argyll, at the time of the contract. She may have been a minor.
The 1642 reference to May Campbell daughter of Archibald, 7th Earl of Argyll, and wife of James, 2nd Lord Rollo, refers to her as the daughter of Anne, 2nd wife of Archibald, 7th Earl of Argyll.
These are of course not original documents, only catalogue entries. Should be checked against the original documents.
Is May a name in use in Scotland at this time or is it a typo for Mary?
Ray