In the latest Legacies episode (S01E16), Hope went to Triad Organisation's place (in GA) to save Landon. After she reached there, Landon told her about Malivore and its/his history, might have mentioned in his story how Malivore was formed/created with Wolf-Vamp-Witch blood.
I suppose after knowing this (Wolf-Vamp-Witch blood thing), she figured out that she is the key for Malivore's end.
But my question is,
How did she know (not guess), that her blood would heal Jossie's wound? It was not her guess for sure because she said to Alaric, "I'll explain it later". There was no way she could have known that Malivore was a creation of tri-breed type blood.
Also, if she knew already, why didn't she give her blood to Jossie herself when they were in the cell, captured by Triad people at school.