My niece wants to do some video editing using Premier and we were wondering if there would be a problem running it on a MacBook Pro with i7 and retina display with only 8GB of RAM? I know 16GB would be better but that is not an option at this point. She is not looking at really large projects mostly just stuff for the internet.
Unfortunately, most if not all of the 8GB MacBook Pro configurations are insufficient to run Premiere Pro at a comfortable rate. In fact, all of the current 8GB MacBook Pros - regardless of the CPU - come only with the integrated Intel HD or Iris graphics. And of those, only the Intel Iris Graphics can use OpenCL for MPE GPU acceleration (the lower-level Intel HD Graphics will result in Premiere Pro being permanently locked into the MPE software-only mode). And even then, the Iris Pro graphics will be slower in the MPE GPU accelerated mode than most discrete AMD Radeon or NVidia GeForce GPU configurations.
Worse, of the current MacBook Pro configurations avilable, you'll need to go for the largest, most expensive configuration (which already comes with 16GB of RAM as standard) just to be able to select discrete NVidia GPU graphics.
As such, you're pretty much stuck between a rock and a hard place (when it comes to currently available MacBook configurations).