She isn't the only one, Valerie is alive as well

@Pavlos Bakirtzis No she isn’t. She is a hybrid just like Lizzie they’re undead and lost their link to the Gemini coven when they were turned into vampire-witch hybrids. Josie is the last siphoner alive and only remaining member of the Gemini coven now that Lizzie was killed by Hope Mikaelson and lost her link to the Gemini coven when she became a hybrid.

However, their are two hybrids still alive Lizzie and Valerie

Her being the Gemini Coven leader would’ve been awesome to see. it would’ve also went well with her dark josie storyline since they were implying that she has a dark side like Kai who was also once the Gemini Coven leader. But since the show ended they didn’t dive into that more with her, would’ve been a good storyline for her if they were to have a 5th season tho. imagine if it were more people from the Gemini Coven alive and Josie was the leader of them all. Not to mention they didn’t even explain how the Merge ritual was created so that would’ve been another thing they could’ve went into if it were another season.