You’ve missed major updates
When you catch up with this friend, you learn major things have happened in her life since you last spoke. They happened a long time ago, and this is the first time you’re hearing about it. Maybe you learn this person was seriously ill for a while, or had an invasive surgery and went through physical therapy. Maybe you learn they had a mental breakdown. Perhaps you learn they’ve been in AA now for several months. Maybe you learn that they’ve quit their job. But, while they were going through that, they didn’t reach out to you. They too go ghost on you during their hard times.