She is initially offensive towards the Dragonborn, refuses to help, and will continue to make insulting comments. She will, however, become friendly towards the Dragonborn, calling them a "friend" once the Glory of the Deadquest has been completed.
Still, after the quest line is completed, Njada may make comments that indicate her displeasure at the Dragonborn's promotion like saying "What guidance could you possibly offer me?" in a rude manner.
When the Dragonborn first enters Jorravskr, Njada will be in a brawl with Athis, which Njada wins. After completing Glory of the Dead, Njada can be recruited as a follower. She offers Expert-level training in Block, up to level 75.
The Dragonborn can marry Njada. This is only possible after completing Glory of the Dead and if in possession of an amulet of Mara.
If either Njada or Athis are attacked while in conflict with each other, nobody nearby will become hostile if one of them is killed.
Occasionally Njada and Athis won't do any damage to each other and just remain fighting, until the area is left. This can be fixed by reloading the last save.
If Njada is married, she may immediately walk out of the temple after the wedding and disappear from the game. The game still considers the Dragonborn married, but Njada is nowhere to be found, even if she was a follower. The only solution is reloading an old saved game. To prevent this, speak with her before she leaves the temple and tell her to follow, where you want to live, etc. (this can be fixed by writing "Player.Placeatme 0001a6d9" then she spawns at that location, the only problem seems to be, she doesn't "know" she's married to you)
The problem reported above (where Njada does not know she is married) is caused by the player.placeatme command - it does not transport the character to the Dragonborn, but creates a copy of it, hence there are two of the exact same characters in the game, and the copy is always in their default state (armour- and relationship-wise). To search for Njada if she went missing, there are two options:
1. In the console, first type prid 0001a6da (this targets Njada even though you can't see her), then type moveto player - this will move the actual Njada that the Dragonborn married to them. (If she for some reason died, this command will not work.) To solve this, first type the prid command, then type resurrect and then give in the moveto command.
2. in the console, type player.moveto 0001a6da (perhaps followed by a 1) - this will move the Dragonborn to Njada's location.
When trading with Njada her helmet does not appear, making it unavailable to remove. (A work around is to give her a better helmet, which will cause her current helmet to appear for sale. Buy it from her, then take back the helmet that was given to her. If all of her clothing is removed in this fashion, her whole outfit will reappear.)
If Njada is previously killed then Kodlak's funeral is bugged/stuck with all characters reporting to be busy. (Needs confirmation)
After the Dragonborn becomes Harbinger Of the Companions, she may randomly stand up and attack them. She can be killed or a calm spell used on her. Neither one will incur a bounty. 1.She can respawn but be seen sliding on the floor
If she is killed and then dead thrall is used on her, if she respawns while enthralled she will not be a follower, and make zombie noises, but will still be 'alive.'
If Njada is the Dragonborn's follower and she dies after they become the Harbinger, after a while she may respawn and dialogue will be possible and she can still be a follower.
If Njada dies before the Dragonborn begins the Companions quest-line, her dead body may be found laying on the floor of the living quarters of Jorrvaskr. Other characters finding her body there will give no explanation as to how the corpse arrived and will be heard saying, "I'm going to find who did this!" (confirmed on X360, but it is unknown if this will occur if Njada dies after the Companions quest-line has been started).
If she is killed BEFORE joining the Companions, she may respawn after the Dragonborn becomes Harbinger. (PS3 confirmed)