Nina was able to conclude that Stella was going through depression, grief and guilt, possibly associated with drug use, all from a fleeting facial expression, reacting to something Jayden's mother said. This is much too far-fetched to be reliable.
There was no practical point in the team taking Jayden to the drug dealer's address where he said Kelli Parkman was headed. He'd never been there and Remy pointlessly asked "Are you sure this is the address?" Jayden is a minor and it was reckless to take him to where they were going to look for armed suspects.
Remy had earlier, condescendingly told Barnes to "Stay close but keep your distance" [sic] when tailing John Parkman's car. In a later scene, she says "I'll tail him." Remy again needlessly says "Stay close" but adds "We'll meet you when you get up there." They can't do that because they have no idea where Parkman is going. That was the whole point of tailing him.
Remy advises Barnes (who is about to tail someone) "Stay close, but keep your distance." She can't do both. Moreover, it is very condescending of him to tell her something that, as an experienced agent, she knew already.