Thanks Helen, I think you have completed some great research on this problem.
However I'm more inclined to suggest that we don't merge the 2 profiles, but move towards making them into 2 separate Catherine Pakenhams. Leave Pakenham-10 as the Duchess of Wellington, and make Pakenham-33 into the possible Mrs Lloyd. Disconnect her from current parents, and make as uncertain her dates of birth and death?
We would need to put some notes on the biography to explain what has been done, and not to merge with Pakenham-10 until more research has taken place.