Andres,
A subVI of a main is not intended to be stopped from its front panel. The only way this should happen is if you are spawning the subVI. In this case, your code in the subVI should have a mechanism for stopping the execution of that SubVI. If you have any outputs from the subVI, then when you stop the subVI, the data will then, and only then, be available to the main.
The abort button should definitely not be used in this case. I also don't recommend using VI Server, but this depends greatly on your specific need.
If you still aren't sure what to do, please explain exactly what you are trying to do, why you need to stop this subVI, and we can better help you.
Good luck