Admissionado
You want to be as honest as possible with this question, but at the same time the ideal situation is when the other schools you mention are ones that are a similar rank to the school that is interviewing you. You don't want the interviewer to think their school is a reach or a safety. If you do have an admit & the interview directly asks you where else you applied you can mention the admit (although I wouldn't proactively bring it up). Depending on the rank of the school though it can either help you or hurt you - if you have an admit from a higher ranked school, the interviewer will assume you'll go there. If it's from a lower ranked school, its actually a better situation since you can easily make an argument why the school you are interviewing for is still your #1 choice. The ideal would would be if you admit is from a similarly ranked school (although that is not necessarily a guarantee of any funding).
Thank you so much for answering!