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Further to your question, unfortunately her visa has been denied.
Yes, you will need to mention the denial as the Home Office already have a record of the same. and if you fail to mention the same it will be seen as deception and could lead to a 10 year ban
Kindly note that when you apply for the spouse visa, you are applying under a different route and as long as you meet the requirements the visa will be granted
The previous visitor visa regusal will not impact the application