The question implies that there is the only computer John and Jane work with ("she work with the same computer"). Nevertheless, Jane will not see the infobase created by John. Here is what is said on this topic in the Lesson 1: "What you see here is just a list of “shortcuts” created locally to remember the infobases you use. Moreover, this list is user-related. Every user will see his or her list in this form."
The first thing you see when you run 1C:Enterprise is this "shortcuts" list. 1C:Enterprise reads this list from this file: "C:\Users\<UserName>\AppData\Roaming\1C\1CEStart\ibases.v8i", where <UserName> - is a login name of a current Windows user. So, when John logins to computer and adds an infobase it is added into file "C:\Users\John\AppData\Roaming\1C\1CEStart\ibases.v8i", but when Jane logins he will get the list from the file "C:\Users\Jane\AppData\Roaming\1C\1CEStart\ibases.v8i". These are two different files, therefore Jane won't see the database John added.