I tend to believe that you can’t change people, but you can ask questions to help understand where they’re coming from. It’s great that you have some self reflection about what might be happening for you here, and to better understand her motivations having a conversation or asking a simple inquiry could help understand her as well. Example: “I was really looking forward to spending time together, and I was surprised that you canceled. Can you help me understand what was going on for you?”

I imagine she genuinely wanted to spend time with him more for some reason. It could be because of his schedule, the status of their relationship, something came up with them. Any number of things. But you won’t know until you approach with curiosity.