The description in your question about your services seems to indicate that your wife and yourself have two independent subscriptions to iCloud+ and therefore no connection.
For her to share your iCloud+ space you will need to Set up Family Sharing and she will also need to choose to use your storage space. This will mean terminating her storage plan.
Apple describes how a family group shares storage space in Share iCloud+ with your family. An important point to note here is under the paragraph Switch from your iCloud+ plan to your family plan
If a family member is already paying for their own iCloud+ plan, they can choose to switch to your plan or keep their own and still remain part of the family. When they switch to the shared family plan, they get a refund for the remainder of their personal plan. They can't keep their current plan and use the shared family plan at the same time.