The fearmongering on this site is out of control at times. Literally anything you bring up will have 1/3 of the posters saying to dump her or that it's the beginning of the end.
I agree it is sometimes unwarranted, but at the same time, her behavior will not improve.
You are right, where it is now is totally fine, but this is the very beginnings of things not being fine and unfortunately it is passed correction.
The password thing is a major issue in relationships, like the point is to trust, you don't entertain a middle ground, you either trust or don't... I have said in the past, on other forums, that auditing trust is OK, but I have come to recognize the audit as insecurity over time, it's just silly.
The emotional attachment is the bigger issue here and she exposed him with her test.
Snap Chat is an innately deceptive application, it is intended to be deceptive... We will all have our opinions on it, some are OK with it, others are not, but it's undeniable that Social Media makes maintaining orbiters easier, but again, if we try to impede orbiters, it can come off as insecure, so we make that conversation about her behavior, the guys will orbit regardless, but if her behavior goes unchecked, then OP is just coasting on his SMV or his provisions, maybe a bit of both and he can do that with plates.
But anyways, my point has been made, I don't want to derail into what is good and bad in relationships all that much because if it works for you, that is great; relationships are anecdotal, but OP came for a reason and he'll ultimately have to make that choice and if he lets us influence him into a bad choice, it's still on him.