Yep. TMP is basically like, "We're gonna make Spock look and act nothing like what he looked and acted like before, and have lots and lots of continuity problems which we are very much aware of but we're making them anyway, while at the same time saying that it's all exactly the same. But don't you dare call it a reboot! It takes place in the same universe! Really, it does!"
Because that's how Star Trek has always handled inconsistencies.
You're a very funny guy.
There is a two-and-a-half year period between the end of Turnabout Intruder and TMP where we know nothing about Spock's life and what he was going through. For all we know, he took that time to ponder his life among humans and decided that he had some serious problems with the way he should be acting as a Vulcan. A mid-life crisis, if you will. Now by that logic, T'Pring could go from being the sweet, caring, level-headed person we see in SNW to the conniving bitch we see in Amok Time, for no other reason than to separate herself from the man that she clearly loves in SNW to the man she clearly doesn't care about and could care less whether he and/or his best friend dies so that she can be with some other schmuck. But do I really think that this character that we're clearly meant to like is going to devolve so easily? I prefer to think that these two women are not in fact the same person because of the fundamental differences I see, but I have no problem accepting that Spock has gone through a maturity phase of his life and has determined that he needs to set a better example for himself as a Vulcan to his people. And T'Pring is only one example.