You probably mean "Sheets" instead of "Tabs".
Anyhow, whenever you select something in QlikView, all other affected views get automatically updated to reflect the change. The fact that you have a graph in one Sheet and the selection was made in another doesn't really matter. Sheets are just a way to logically separate the information presented to the end user, but you do NOT have a separate environment in each sheet. In other words, what you do anywhere in Qlikview will affect all your objects, regardless of which sheet they are placed in.