After watching the last bit of this cutscene multiple times, I think Eris Morn might be evil... but that's just my opinion. It might be Bungie's lack of story, or maybe they're going to go more in-depth about it in Destiny 5, or just stuff it somewhere in the Grimoire because they're too lazy to make more cutscenes, or something. Anyways, tell me what you think. I honestly think she's trying to help the Queen pursue her potentially evil goals.
There's speculation to believe she's taking over for the queenin her absence, and that the opening cut scene the queen was talking about eris and how they knew each other before.