I don't think you still fully understand. It is not the permission to stay date that matters.
It is the date the orignal O-A visa stamp has for an expiration that matters.
Say for example she had obtained the visa in July 2024, it would expire in July 2025. Even if when she entered Thailand she received permission to stay until August 2025. After July 2025 she could leave Thailand without getting a reentry permit and it would kill off the permission to stay and she would have to obtain another visa then or come back visa exempt.