Sometimes when they don't understand the reason themselves children grasp at whatever idea they can, like saying she doesn't like walking. Sometimes people can hold it together for something special. Her making it in those days doesn't mean there's no issues. It great you've been fighting for her, it sounds like you're understandably worn out on it, but don't take a couple days at these events to mean it's all BS and there's no issue.
My DD has anxiety and is Autistic. Regular issues with school refusal since kindergarten. She missed 3 days one week last term because she felt she messed up an oral presentation, went in the fourth day, to do her band concert I thought thank god we're through that but then the next week was off for two more days, then a couple of half days. Anxiety doesn't always make sense.
It's not necessarily as simple as busy and noisy is always an issue. Maybe she got her courage up but then something happened so she was off again. Maybe she had extra motivation to push through those 2 days but that exhausted her. Little things others might not even notice can derail DD, she takes everything to heart, she feels everything deeply, she misunderstands social situations and gets upset because of it. Many of these things she can't articulate, she doesn't even always know when it's anxiety and not a physical illness. Her anxiety often comes out as anger, she scream at her siblings for looking at her, she'll physically hit out.
I really don't think the things your DD is doing mean you've wasted your time and energy fighting her corner, there is something going on for her, there is something she's struggling with. I wish I had some solution for you, it's really tough what you're going through and I can see you've tried lots of ways to access help. All I can suggest is part time attendance might help to get her back to school.
School refusal and anxiety are exhausting and it wears away at you, saps your strength. Just getting DD to her classroom door some mornings leaves me utterly spent. I can't face being near people for a few hours after one of those mornings. She goes through bad patches where it's constant and its so damaging to all of us. When things are bad I have to stay close and she can't cope with her Dad, so the more she's struggling the more I have to carry and the more I struggle. It's bloody hard and worse if it's just you carrying it all.