There is no reason to think that she intended it as some kind of 'rebellious' statement or disobedience to scriptures as some have supposed.
I don't think anyone has said she intended to or was making a rebellious statement. However, what she did (her outward testimony without speaking a word) does reveal a lack of knowledge of what scripture tells us is to be our way and actions. And it has been noted by scripture that those in ministry are held to greater accountability as they should 'know' The Way as laid out in scripture by revelation of the Holy Spirit before going off to minister, else what they minister comes from somewhere else other than HIS spirit.
Again, those in ministry according to scripture must know HIS ways before they go a ministering. Those who do know discernment through seeking HIM in spirit and in Truth through holy scripture can SEE...have discernment to know the difference. It is then not the person who is doing the judging, but the person looking to the word for alignment. When something does not line up with the word of God, then it is contrary to God.
We who genuinely believe are all undergoing a process by the Holy Spirit that unctions us to seek HIS ways and by doing so, learn discernment of what is from The Spirit and what is from the flesh (human understanding).
Getting up to sing a song as a layperson is one thing. To be in leadership of a music ministry (or any public ministry)
has strict requirements according to scripture. The OP addressed this matter using scripture, or held the person's action up to the LIGHT and it revealed something that was not LIGHT.
When someone is in public ministry, they are sowing seed. That seed either comes from the spirit of LIGHT, Christ, or it comes from the flesh and human mind. Therein is the problem. Therein lay the reason public ministers are held to higher accountability...they are spreading a message that is contrary to scripture. Everything that person in ministry does must align with the Cornerstone, again,
according to scripture.
It is quite distressing that so many are pointing the finger at the writer of the OP and all who by the grace of God see the lack of LIGHT in the action. If the girl with the shaved hair were a lay person, it would not be regarded in quite the same way. Those in ministry who do not know The Way have no business out there trying to point a way that does not align with scripture. See the difference?
Now, the judgements being passed upon those who have held this ministry up to the LIGHT reveal something, too. They appear to be coming from a lack of understanding on what scripture truly says about judging. We either judge according to
our own perception or according to The Spirit (that always aligns with scripture.) ADDENDUM: Then, it is not the person judging, but The Word of God. Again, see the difference? If you question what that person is saying, look to SEE what scripture is saying and then compare the persons word/action to scripture, not human perception/understanding.
All we have to do is look at the world around us to see the lack of LIGHT in it. We are to be salt and light in a dark world. If we say and do exactly as the rest of the world, then we are not being that salt and LIGHT. We walk in the darkness like the rest of the world, not being set aside apart as scripture says we should.
Reading the Bible is so important and part of seeking to find out what HE says we are to be and do, then doing it by faith. Anything else is unbelief.