She is recruitable after obtaining the Topaz of Earth.
Jeanne is a decent character, she has 20 Strength and Will and 19 Magic, her Charm is 22 and her other statuses are 16. Her speciality is the Spear, but she can do well with Katanas.
Speaking of Katanas, she is one of the two non-Gerard characters that has a cosplay item, the Moonlight Sword changes Jeanne to Kremhild, the Last Empress from Romancing SaGa 2.
Kremhild is overpowered, spotting 20+ in all statuses, just like Orion.
Jeanne is good with or without cosplay item, giving her a try isn't a bad idea.