Hmm... [He thinks about it. The easiest way is to become friends with the other idol, but that isn't really an option here. So what else?]

...If she works for a production company, you should be able to just look that up. You could look up magazine articles too, but a lot of that is made up, or her production company controls it. So, it might not be helpful. Also, they probably hide her address, so the fans and press won't bother her at home.

If you can't get information from her agency... a lot of stagehands gossip. So maybe they can help.