8GB is pretty low for this game, but that mostly affects FPS or loading rather than lag. Of course, sometimes FPS or loading speeds get called lag. If you are referring to lag in the sense that someone does something and it takes a second or so before it actually happens, then that's usually going to relate to some network problem and not the OS or RAM directly (though possibly indirectly). If you are referring to things loading late when moving around (such as cars popping up out of nowhere on the roads of a city), then that's the computer and not the network.
If it's related to the network, you can try using the Network Workaround option in the game settings on both computers to see if it helps. Alternatively, try switching who is hosting the game. You could also see if the problem occurs on a dedicated server. Also, look at the pinned topic in the General Support channel to see things you can do to help, such as making sure you have the game excluded from antivirus for both the game directory and saves directory.