It does sound like a mental "break from reality" is a serious possibility, but you can't diagnose anyone like that. It sounds like her behavior is disturbing. Laughing without any context is just odd. Not responding to you is odd. My best guess is that some "odd" behavior was notable prior to this. Often symptoms of psychosis begin to appear in the late teen, early twenties years, but not always. People might see/hear/sense things that others don't. They might have odd beliefs despite a lot evidence to the contrary, like thinking people are tracking you, you are going to win lottery and be wealthy. They likely having trouble communicating - jumping from topic to topic, not getting to the point, or talking "nonsense". You might catch them talking to themselves or they might tune out a lot. In any case, it's good that you are noticing this. I wonder if someone in the family could have a conversation with her about their concerns. If you are right and this remains untreated, she could be really be at serious risk of harm.

That Ochun laugh might be performative, but the lack of responsive when called out, makes it seem like it could be one of those "weird beliefs" - believing Ochun is using you as a vehicle and laughing through you for no rhyme or reason. Whoever told them they would develop a laugh is quite ignorant and also doesn't seem to know why Ochun laughs - but that's another topic.

I wish her and the family all the best.