In Elden Ring, there are too many connections between 
Melina and 
Ranni to ignore, from the knowledge they have to the aid they provide to the Tarnished Champion. Meanwhile, they both hunt for their purpose outside of the influence of the Greater Will. When they're examined closer, it's possible that there's more of a connection between Melina and Ranni than players realize.
[Warning: This article contains spoilers for Elden Ring.]
Elden Ring takes place in the Lands Between, which is ruled by Marika the Eternal. After she shattered the Elden Ring, the Greater Will punished Marika by trapping her within the Erdtree and using its Grace to guide the Tarnished Champion back from their exile. The Greater Will hopes for the Tarnished to re the Elden Ring and take up the mantle of Elden Lord so that the Golden Order may continue. Assuming the role of fake Finger Maiden, Melina turns runes into power for the Tarnished in order for them to grow stronger and complete their journey to become the next Elden Lord.
As Elden Ring tends to hide lore to make players search for answers, not all of the connections between Melina and Ranni are straightforward to find. The first connection that the Tarnished comes across is that the spectral face ed to Ranni's doll face is identical to Melina's face, even including the marking over her left eye. Their connection is reinforced when Ranni mentions that she knew Torrent's former master, just like Melina did, implying that they both must have been close to Torrent's unnamed former master. Both women go against the Greater Will. Ranni refused to remain an Empyrean and searches for her own path. Melina, too, is searching for her own path, but she shows her opposition to the Greater Will in her willingness to be the kindling for burning the Erdtree, an act she calls a cardinal sin.
Elden Ring Theory: Melina Is Ranni's Forgotten Sister
Elden Ring's Queen Marika, mother of demi-gods, is Melina's mother, making Melina a demi-god and, therefore, Ranni's sister. Melina's dialogue heavily implies that Marika is her mother because she says that she was born at the foot of the Erdtree and that her mother is within it. If that isn't enough confirmation, the game files for her dialogue label her as the daughter of Marika. Aside from their direct relation to Marika, Ranni and Melina share another - more specific - quality. They are spirits. While Ranni willingly cast aside her flesh and opted to possess a doll's body, it's unclear whether Melina ever had a physical body. It's only confirmed that she doesn't currently have a body, instead of being a soul who needs the Tarnished to help her travel to the Erdtree.
Whether the Tarnished gets Ranni's mistranslated Age of Stars ending or makes an enemy of Melina through choosing the Lord of Frenzied Flame ending, the Tarnished is able to learn about Melina and Ranni through various quests and conversations leading up to these two Elden Ring endings in particular. Though Melina is with the Tarnished through most of their journey in the Lands Between, very little concrete information can be obtained about her. She may be the other half of Ranni, much like Marika and Radagon are two halves of the same person, or Elden Ring could reveal Melina to be the mysterious Gloam-Eyed Queen.
