Did not declare travel partner in UK visa (business trip). How should I respond to immigration officer?
Upvote:4
It's best not to approach immigration together. Immigration prefers to process people together only if they are related in some way.
You do not have to explain anything about that. You won't be asked, and the explanation that your friend decided to travel after you had made your application should be sufficient.
The only things necessary to getting your friend through immigration is to establish that she has the resources to support herself, she will leave when she says she will, and that there isn't anything strange going on. As an American your friend is unlikely to be asked about her finances. If she is she should answer truthfully and if necessary get you involved. It would be a good idea for you to have documents with you to prove you can afford to make this gift, including bank statements.
Another thing you should be prepared for is some questioning about why you are doing this? Because it is very unusual for people to pay for an entire vacation for people who they are just friends with.