Ah, OK, you're not famiiar with his backstory. Cassandra found him and knowing he was pre-immortal and raised him as her son. He saw her killed when he was 10 when she wouldn't tell the chief where Hsu was, and he ran away, thinking she was dead. They didn't meet up again until a few years ago. He didn't know she was immortal and she didn't think he'd survived in the desert, as immortals do not become so (except for Kenny, the exception to prove the rule!) until they've 'matured'. So she didn't think he'd survived, making her lose faith in her own ability - the 'Vision'.

So it's possible to have her resume her revenge rampage in wherever, teach Quinn, then Quinn to go off on her own, and end up meeting Hsu. There's about 20 plus years between her and Hsu parting and him being killed, and then becoming immortal. Not sure what other plans you all have, but yeah, it's possible.