What do you mean? Maya Sundaresh doesn’t seem particularly “not nice” in the grimoire; she consistently seems concerned for both her team as a whole and her wife:
SHIM: Once we try to make the call, the Vex may…react. So let’s all savor this last moment of stability.
SUNDARESH: [indistinct sounds]
SHIM: You two are adorable.
Maya Sundaresh walks at the center of the group. She’s been too quiet lately. What happened to them wasn’t her fault and maybe she’ll believe that soon.
Cayde was obviously in her lab for business, so there’s no real reason for them to be chatty:
But she’s already turned back to her work. I shuffle my feet, straighten my back, and return to mine.
And given the fact that it’s pretty heavily implied that he was in love with her (from both the Book to the scan in his Stash), it’s little surprise that she would be uncomfortable- she’s already married to Chioma Esi. Cayde, to her, seems to be a fixture in her lab because her work needs protecting; Cayde is going to see the situation differently because he has some amount of unrequited love, and as a result her not talking to him may feel more personal than it really is.
From the Exo card:
Many of the City’s Exo citizens live and work alongside their organic brethren. But others fight again, re-forged in the Light of the Traveler to serve as Guardians.
So there are Exos in the City, even if they’re not very present in the Tower itself.