You need to separate naturalisation from the passport process.
It would be easiest to apply for naturalisation under the name as per original passport - once British she could then get a British passport in that name. OR before that arrange an official name change by Deed Poll and then apply for passport in married name. Refer to
https://www.gov.uk/change-name-deed-poll. I know people who have done that in different circumstances and it seems quite straightforward. As for legal opinion I can't make any recommendations - overall naturalisation is a straightforward application as long as the requirements are met. Normally you would not use legal advice to apply for a passport which comes after naturalisation.