I've encountered this particular use in Greville Fane (1893) on two different occasions and am quite perplexed by the actual meaning as none of the meanings for that idiom given by the dictionary seem to fit very well:
- I spoke of her to the lady I had taken down, but the lady I had taken down had never heard of Greville Fane.
- I met her at some dinner and took her down, rather flattered at offering my arm to a celebrity.
The idiom dictionary lists 2 seemingly relevant uses:
- To lower someone's arrogance or self-esteem: The opposing team really took him down during the final game. They were so good that they took down each member of our debate team.
- To write something one has heard or observed: I took down every word they said so I could review the conversation later. The stenographer took the speech down and transcribed it.
1) does not seem to fit the meaning. There seems to be no malice in the speaker's words, and he stated that he "liked" one of the persons that were "taken down" by him.
2) seems like it could fit. The narrator is a journalist, so I can guess that "taking down somebody" could mean interviewing that person, but I'm really unsure, as no example in any dictionary backs up my theory. All examples I could find are similar and mention "taking down" something like a speech or a conversation.