Self-absorbed people like to one-up others. They don't like the focus being on anyone else's distress, projects, or goals.
If you tell a self-absorbed person what you have going on, they will tell you about something bigger they're experiencing or doing. This could be positive or negative. For example, if you tell them about your COVID vaccine symptoms, they will no doubt have had more severe symptoms. If you tell them about a craft project, they will tell you their plans to renovate their whole house. If you tell them about a success, they will tell you about a bigger one.
Because self-absorbed people get very immersed in their feelings and endeavors, they can be inconsistent in their contact with their support people. They may want to talk to you often if they're excited and see you as an outlet for sharing that excitement. However, when they've moved on to another topic, they might move on to another person along with it.
If you're not fulfilling a particular need for them, such as a need for emotional support, they may all but disappear. They may become very interested in you if they sense you may help them with a goal but then go "off" you if that doesn't pan out, or a new person catches their attention and seems more valuable.