[Vuejs]-How to access a Vue inside another Vue?

You should try using a state pattern (check vuejs doc Vue.js State Management Guide)

Basically, you create a data object and allow your instances to "share" it.
Therefore, you can access and mutate this object from those instances, and it behaves in a reactive way.

If your application grow up, you should evaluate using vuex (Vuex), which helps you with some issues you may find when working with state management, such as painful debugging.

Hope this helps you!