I have ADHD and I agree it's better than the real world
It may be frustrating if she wants to see a specfic band, she will highly likely get distracted - unless you help her to plan
I'm not an expert, and I'm sure the condition manifests itself in different ways, but my friend who had ADHD absolutely loved Glastonbury and said it was loads easier than the "real world". Hopefully your wife feels the same 🤞🏼