Get in and stay in.
Your standard ground approach tool would be Shining Onslaught or running in to do normal attacks. Or you can wait and punish whatever the opponent tries to do with Holy Ladder or Noble Strategy. If you still have a lot of health, Königsschild parry is also usable in neutral if you can predict what is coming.
Against zoners and characters with longer reach, be mindful of the range where Noble Strategy and Holy Ladder will work. Punish the recovery of their big moves with M/H Shining Onslaught.
When opponent is in corner, put the pressure on with your standard mix-up into Sword of Lumiel to maintain frame advantage and stay safe. Opening opponent up with Noble Strategy may require a bit of hard read and some careful spacing, since it puts you airborne and all versions have slow startup that you may get poked out of it. Remember that throws, 2U short-range low sweep and Overhead Attack exist.
After Charlotta gets a knockdown, the choices for okizeme really open up. Ground/Air normals, throws, Noble Strategy, or Sword of Lumiel meaty if you want to buy more frames.
Getting out out corner can be difficult due to Charlotta's attack range. Use Holy Ladder to stop jump-ins, Noble Strategy to make people whiff (although risky), Königsschild counter if you still have health or rely on Brilliant Moon to punish moves.
Be aware of your special moves' cooldown, since lacking any of them greatly impedes Charlotta one way or another (No mixup, no plus frames, no fast advancing tool, no AA or several of them at once) Consider the game state (Neutral or corner? Distance? Skybound Art of both sides?) and options you will have after you use a special move.
Click [★] for character's full frame data