In the first game, while it is common for the game, The Last of Us to give players some companion, they do not really help make the game easier for the player as they don’t really do much other than follow you around but according to Naughty Dog, the companion in the new The Last Of Us Part 2 will have the allies do more in combat.
According to the developer, players will spend some time alone but also some time with a companion and that this time, they can actually do more than just follow you. The demo showed Dina being able to perform a stealth kills on her own. It was added that they will be able to help you out and rescue you in some situation.
Naughty Dog has made it a point to make all the characters in the game more realistic and that includes allies and enemies.