Really? Because I can think of any number of reasons to mistrust Maria- shapeshifted infiltrator, LMD, brainwashing, geasa, good old-fashioned blackmail... all of which could help to explain why Maria is pretty much not acting like the trained agent she should be. Heck, this issue seems to establish that Maria *is* fumbling about partially due to post-mind control trauma... and I'd think less of Natasha if she wasn't at least considering 'if Maria was mind controlled, is there anything else still in there, besides natural trauma?'
And Natasha *is* trying to help Maria shape up- yes, she gives Maria a hard time for her recent behaviour, but it's also an accurate assesment as to what's wrong. She *then* follows up by saying that Maria can do better, has done better, and if they're going to carry this mission out, that's the Maria they need.
Bucky and Luke Cage would be distrustful, because they were/are on the other side, thanks to the Registration. Natasha is suspicious because that comes with the job.