Lady has the lowest HP of all of the final bosses, but she has her strengths. She is weak to all elements but also absorbs them, meaning that all forms of elemental damage will heal her. Lady frequently casts White Wind, healing herself and Rest for several thousand HP. If Rest is killed Lady will cast Arise to revive him. Fortunately, Arise will not heal Rest to his full health of 40,000 HP due to the damage cap, and so he will be revived with 9,999 HP. For these reasons Lady should be defeated first using non-elemental spells like Flare and Ultima.
Note that a Ragnarok can be stolen from Lady, in case the player chose the magicite for the Ragnarok Esper. However, the sword cannot be kept after the final boss in the SNES or PSX version and is only useful for the rest of the battle.
Lady's Japanese name is Maria. Due to religious sensitivities, the name was changed to Lady. [view·edit·purge]Maria is a female given name in many diverse cultures. It became popular with the spread of Christianity as a Latinized form of the Hebrew name of Jesus' mother Mary (Miriam in Hebrew). The meaning of the name is uncertain, but it may originally be an Egyptian name, probably derived from "mry" (beloved) or "mr" (love) ("eminent lady" or "beloved lady"), although it was used in Europe even before the establishment of Christianity as a female form of the Roman name Marius.
In Latin, maria can be roughly translated as "from the sea".
The English SNES version of Final Fantasy VIcensored the appearance of Lady, altering her veil slightly to make her breasts less noticeable.
In addition, the fight with Lady (Maria) and Rest was an allusion to the Pietà, a sculpture that depicted the recently-deceased Jesus Christ post-crucifixion being cradled by the Virgin Mary, his mother.
The Virgin Mary, when depicted in a devotional image, such as those of her cradling the baby Jesus or deceased Jesus, she is more commonly known as the Madonna, where she will often have a halo. Madonna translates into English as "My Lady" or just "Lady."