Is it appropriate to confront a higher rank when they are blatantly disregarding regs?

This is one of those things that people that should not nor ever been allowed to have been in the Military just do not care about, Even worse Seem to have problems doing the right thing.
REGULATIONS are the for a reason. Whether you do or do not agree with them.

Regs are there for a reason, if she was out of uniform and off duty, no problem, but in the mess hall and in uniform she could have been written up for being out of uniform code Just like if a man had his hair too long.

Absolutely! I hope that my relationship with my soldiers is solid enough that they feel comfortable correcting me as one professional to another.

Yes you should with tack and discretion. I have on more times then I can remember telling higher ranked people how their uniform's had problems. People thought that I out of my mind when I walked up to my AIT CSM asked him if I could speak to him. He looked at me like was out of my f**king mind. then he said what l told him that His collar was standing up in the back, And his boot laces where hanging loss. He leaned forward said thanks. I turned around and left. My Drill SGT called me in to his office later, Then informed me that I would not be pulling fire guard any more. That was the first time. Other time have not gone so well, However you should always try to do the right thing because may be the one jacked up.
Was this at joint base Charleston The amount of jacked up Air force people of all ranks on and of that base.
These types of issues usually come from lax or incompetent leadership.
That goes for all branch's of the Military.

There is a great deal of reticence regarding approaching a person of higher rank in order to make note of a uniform regulation violation. Ideally, the senior person will recognize the problem, thank you (and/or give you one of their coins), and fix the problem without delay. Ideally.

Unfortunately, we have many members who are far from ideal. It is our duty to deal with such people, too. So, here is my recommendation, for what it might be worth.

First, before anything, introduce yourself and identify your Unit. Courteously ask about the other person's unit. Take note of what you are told; this will be one of the most important pieces of information you will get.

Next, ask this individual if they would like to know of a uniform violation that you have observed. Whatever answer you get, take that seriously. If that person says "No" or "Buzz off" or anything like that, do so and be polite about it. Like "Sorry to have bothered you, have a great day." If that person says "Sure. What's the problem?" (or something like that) then you're golden. Just politely point out the flaw and let that person handle it.

Now, if you get a negative response then you have two options. Option one is to ignore it. Option two is to go to your supervisor and/or 1st Shirt and discuss the situation. Remember, you got that person's Unit, so you have some information. If you also got a photo then you have more information. Remember, you are not "getting somebody in trouble." You are just being observant of uniform violations. Listen to your supervisor and/or 1st Shirt. They might say "okay, I'll handle it." Then, done. That's their job. You can breath easy and know you've done your part. Or, your supervisor can refer you to that person's supervisor or 1st Shirt. If that's what happens then bring your concerns to that person.

If your supervisor and/or 1st Shirt won't be helpful, then you have some standing to speak to the Commander. No 1st Shirt wants that, so it's unlikely. But, again, that's the ideal world. In any case, be courteous, present only the facts, and listen to what you are told.

Hopefully you will find this helpful.

I once told a superior officer, offline, that his BDU top didn't match his bottom. This superior officer misunderstood me and threatened to "fix" me under Articles of the Uniform Codes of Military Justice that I would never see daylight outside of Leavenworth. Our difference emerged because I meant the bottom of his BDU and he thought I was referencing his derriere. Can we be charged under Articles of the UCMJ for being helpful to others and for being selfless?

So; I saw an error and as a prior non-commissioned officer I decided to address this mistake. The error was on the uniform of a superior officer. Everyone else ignored the mistake, but not me. I tactfully informed the superior officer in a question, in the presence of the CSM. Realizing the error, the superior officer fixed it and then, gave me a mouthful claiming that my behavior was insubordinate and my action was borderline UCMJ. The CSM smiled and reminded the superior officer that I was only correcting his error for his own good, which is in no way a UCMJ action. As the CSM and the superior officer argued, the CSM signaled for me to peel off, which I did without any delay.

These are the battles of military life; Superior v. Subordinate equation.

I used to have the same problem with my Executive Officer when we were planning operations and he would propose something that went entirely against my Logistics regulations. I would open the update to the first page where it said no deviations and then to the last page and tell him when he outranked the person in the signature block of the regulation then I would obey his wishes.

That was probably one of the main reasons I exited the Military. I respect rank, but can not tolerate anyone who takes advantage of it to cut down or humiliate anyone of an inferior rank, all the while demanding respect of their rank. A Military rank is not a free pass to do or say whatever you darn well please and shouldn't be considered a shield for such coming from the ranks. That clearly falls under the title of 'Abuse of Power or Authority. When Someone wants me to respect their rank, either In the military or their position in the private world, they will EARN that respect and honor.

Several decades ago, I was in suit and tie and noted a command sergeant major parked in a marked handicapped spot. He had no handicapped license plates nor a handicapped hang tag. I walked up to him before he exited his car and I simply asked if he was aware he was parking in a handicapped slot. He began cursing me and told me to mind my own “f**king business”. I then badged him by displaying my CID credentials and asked if he’d like a citation for parking in a handicapped slot. I also told him that I was willing to accommodate him, as an MP patrol was approaching me through the lot. He then sniveled that I hadn’t initially identified myself as an agent and he wouldn’t treated me in the manner had he’d know. That wasn’t my point. I wasn’t going to get badge heavy and simply have him move his vehicle. After his whining, he moved his vehicle.

Yet, it didn’t end. The next day, he had the parking place remarked for sergeant majors only. That left the PX without sufficient handicapped parking places under law. That caused me trip to the IG and a complaint to be filed. Repainted the next day back to handicapped, with a discussion with the sergeant major by the IG. When you find yourself in a hole, stop digging.