What punishment should I recommend for Soldier who showed up for an ASU inspection with it on a hanger?

If the soldier has been in less than a year, she may not be aware of all the policies & rules regarding uniforms. Remembering myself as a new airman who was shy & anxious with no friendly sergeants that I could ask questions of I would counsel the soldier, find out if there are other topics She needs to know about & inform her of where to find out her duties & responsibilities as a soldier, making sure she is clear that asking a question ahead of time costs less careerwise than blundering through at the last minute when there is no time for correction without a ding.

No,
Firstly, you keep saying SHE, the correct term is the soldier, (No Gender).
Secondly, the soldier did as commanded showed up for a ASU (whatever that might be (I am an English serviceman, still in uniform at 82. (forgive for not understanding you terms))) with their uniform.
Thirdly, It was you'r mistake for not stating "wearing"
Fourthly, they need promoting for showing initiative, they knew what you meant,, but turned it around and took you literally,, well done.

Fifthly, I would have said something like, “very good, well done, I appreciate the humour, Now return here in 15 mins wearing said uniform".

Honestly the quick thinking and ingenuity deserves recognition. I'm an old army veteran but this troop adapted and overcome. Bravo, bravo!

Reach down into your "LEADER" skills and tactfully find out WTH is going on and try to help the soldier. You asking about "Punishment" right out of the gate makes me lift an eyebrow.

Ask the 1SG he can help you out; at least it was that way when I was in.

I got the same issue, in Iraq punished for holes in my uniform unable to buy any, barred from asking for any, yet punished the same way. Rifle rubs holes on my huge crotch area, with my blue jeans under them covering up my Underwear full of ❤️ hearts. Was told to wear civilian pants at from all my supply sergeants request to cover up, every time I saluted an officer at Kirkuk Iraq, I was penalized to a sexual orientation class. I never questioned my sexuality until I deployed to Iraq, and watched some amazing Army PowerPoint porno slides. I had six ACU pants ripped from the crotch area. The same thing as rifle birdcage tore many guys' uniforms apart. It didn't take much, one month out there, my blue jeans weren't torn nor hurt as bad under my uniforms. Good old Levis pants made in California!

Wow after looking at some of the senior NCO posts I wish I could reenlist. I would walk all over your get to know the soldiers problem state of mind lol. Do you have any idea what a motivated Spc4 can do with that kind of slack. OMG I would sham all day and have you believe that it was everybody else’s fault but mine. Generation gap for sure but hey I could be wrong maybe if I was coddled I wouldn’t be disabled today.

In my experience, a "uniform showcase" helped to fix the problem. 5 minutes to change into IPFUs (seasonally appropriate), 5 minutes of exercises, 10 minutes to change PROPERLY into Army Greens (back then/ASUs now) for an inspection, 10 minutes to properly stow your Class As and change into ACUs, 5 minutes of exercise, 5 minutes to change from ACUs to IPFUs, and 10 more minutes of exercise. For my soldiers who could not properly fit into their dress uniforms, I put it on paper and came up with a wellness plan (NOT FITNESS...WELLNESS) with their input to remedy the problem. Fortunately for me, they were all barracks soldiers. So the time limits I set worked out great. The wellness plan DID involve extra physical training, but it also involved a strict meal plan in which all 4 of us ate and trained together. After the 18th day, the soldiers started getting extra work on their own AFTER we would finish working. It was pretty involved, but I believe that is what it sometimes requires in order to reach success. Best of luck with your troop, battle.

Smoke session

Give her a counseling statement, get her issued a uniform that fits, and have her report for duty wearing her ASUs for 5 days straight. As the ASU is an issue item - she should be able to DX it with supply. If she has to buy a new one - that's punishment enough.