Dark Inferno is a different move, making Dracula Phase 1 and the Witches the only two enemies with two moves Charlotte can learn. Dark Inferno are the balls of energy, Hell Fire is the multiple fireballs.
Technically Dracula Phase 2 has one too, but it's Ghost Chaser, which you can learn fro Dullahan as well. Phase 2 Drac just uses them in volleys, giving you a higher chance at learning.
Charlotte can learn:
Acidic Bubbles: From the Gargoyle Dogs.
Dark Inferno: Dracula Phase 1.*1
Death Scythe: Death.*2
Demon Seed: Man-eating Plants.
Energy Flow: Witches.*1
Featherblades: Harpies.
Fireball: Bone Pillar.
Flame Shot: Fire Demons.
Ghost Chaser: Dullahan, Dracula Phase 2.
Heal: Witch.*1
Hellfire: Dracula Phase 1*1
Ice Fang: Sea Demon
Ice Needle: Frozen Shade
Nightmare: Malachi
Piercing Beam: Nova Skeleton
Poison Spores: Moldy Corpse
Raging Fire: Skittle Bones, Minotaurs, White Dragons. Tough to learn from Skittle Bones since they move around while using it.
Sickle Moon: Imps
Splash Needle: Merman
Summon Gunman: Skeletal Gunmen. Bind their bullets they shoot, even though you can't see them, it'll still count it.
Summon Skeleton: Skeletons
Thunderbolt: Thunder Demon
Every spell you absorb helps boost up Charlottes INT and ATK, meaning more physical and magic damage/healing power.
*1 Even though they use two different spells, you can only learn one per enemy, so only try to get what you want/need, rather than both at the same time.
*2 Either from him flying around harassing you before the boss fight, or during. Either works, but it still counts as learning it from the same Death, so only one chance per run of Chapter 5. On the other hand, this is good for just farming it, because you can run to the clocktower, which is basically the next area after the spawn hallways, learn it, then jump on spikes to die to save.
Basically, I run around with Flame Shot as B, Energy Flow as Up+B, Piercing Beam as Forward+B, and Heal as Down+B, unless I'm doing Chapter 2, 4, or 6. Then I replace Piercing Beam with Deathscythe for shotgunning Puppets going in to Iron Maidens, racking up fast damage on Brauner before he starts doing Blood Arts, and taking down Final Guards fast.