For non-parent-child relation, then this is the same as this one. Call one method, apparently any method of a component from any other component. Just add a $on function to the $root instance and call form any other component accessing the $root and calling $emit function.
On First component
....
mounted() {
this.$root.$on('component1', () => {
// your code goes here
this.c1method()
}
}
and in the second component call the $emit function in $root
...
c2method: function(){
this.$root.$emit('component1') //like this
},
It acts more like a socket. Reference here
https://stackoverflow.com/a/50343039/6090215