I don't care much about the box thing.

A few anecdotes here and there from people who know supposed INFPs who dislike boxes doesn't really hold up well in the face of typology communities filled to the brim with INFPs who readily embrace the label. We are possibly the most populous type in these communities. Isabel Myers herself was an INFP and she invented this system to categorize people!
So no, it's not an "INFP thing" to reject all forms of categorizating.
What I don't like is to have people ascribe me bad motive because they jump to conclusions about what certain behavior or choices must mean. Maybe that is what your friend means by boxes she doesn't like - making negative assumptions about people because you reduced them or their behavior to something overly simplistic and didn't consider alternatives. Not considering alternative interpretations rubs Ne the wrong way. It's not asking you to defy logic....it's saying to widen the scope and perhaps realize you didn't have all the data points to draw an accurate conclusion with your snap judgement.
The way I see people use boxes is often
illogical. Their reasoning looks like this to me:
"People who wear purple often seem to like pancakes. You wear purple. You must like pancakes."
Another form is majorly projecting:
"That purple colors grabs my attention. You must be wearing purple because you're an attention whore!"
"If I wore purple, then it would be because I am rebelling against what I feel is a more mature choice of grey. That person wearing purple is so inappropriate and immature."
So to me, it's just a lot of stereotypical BS. I don't think people actually,
consciously use crappy reasoning as shown above, but I think they jump to a conclusion about something as if it's an unquestionable reality and not an
interpretation which has possible
bias in it.
Obviously your frienemy uses SOME categories or she wouldn't identify as "intuitive" or assign colors to flowers. Language itself defines and categories. But don't point that out to her if she feels like your correct and criticize her a lot.
I suspect there is far more to this, and sometimes IxFPs give up on explaining their whole view or never attempt to begin with because they don't want to be that vulnerable. In other words, "I don't like boxes" might be some stock phrase she goes to out of frustration, not bothering to detail what value was actually violated and how. Perhaps that seemingly protects the value even more (by keeping your nose miles off its scent) and also saves a lot energy. Getting people to grasp your reason for something (because feeling is reasoning - oh yes it is!) often requires them to majorly shift their perspective at the same time. It asks them to change their premise, which is often a bias about what reality is like, something that can make them feel threatened to question. So instead of going through all that, a flippant response to basically tell someone to STFU seems preferable.
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Anyhow, I have clashed with an INTJ who is an enneagram 1 and quite a different animal than the enneagram 5 variety (who I usually get along okay with). To me, he has a "my way or the highway" attitude, but then gets all pissed off when people choose the highway. He also jumps to the worst conclusions about people. He gives no benefit of the doubt and has zero empathy. Also, if something annoys him or seems wrong to him, it is addressed as if it is an objective standard and not a particular
preference or
viewpoint of his. Yet, when it comes to his flaws, well, people should forgive and laugh it off. He doesn't seem aware he even has flaws though. The double standards get to me, and when you have that big of a stick up your butt, you really don't have room for double standards. Confusing preferences for objective standards is another annoyance of mine. It makes people inflexible and unreasonable to me. I don't bother to reason with him because he gets so butthurt. He is so stubborn, that I feel like I end up attacking him personally to get his mind to open a smidgen. He can't handle being wrong ever, and the only way to get him to see another way is to be like, "YOU ARE HURTING PEOPLE" and then he overreacts to the idea that he hurts people... So instead I mostly ignore him.
I'm sure this INTJ's take on our personality clash is quite different. He might tell you I am rebellious, disruptive and unreliable. He would think this stems from arrogance and carelessness on my part. But that's because he ascribes the worst motive possible for everything. To me, he comes across as a miserable person who wants to make everyone as joyless as he is. Most of this reeks of unhealthy enneagram 1, and my being a 4, that seems more at the heart of our differences than Jungian type. I seriously thought this guy was ESTJ because the e1s I've encountered before who were like this happened to be ESTJ, but he tests and identifies as INTJ, and he does display intuitive preferences at times (ENTJ still seems a possibility).
I mainly brought this up to illustrate how an issue looks very different from the other side...