Rosary beads are a big help in this fight, especially as you are learning her attacks. Simply use Debla, and you will i-frame the entire attack while dealing solid damage to the boss in return. Notably, when the 3 enemies merge and do the massive laser attack, you want to actually stand right above them for this strategy. This means that with drop of coagulated ink and heart of cerulean incense you can worry solely about positioning, and then fire off a Debla when the 3 targets are in a similar position. While you are using Debla, you do not take damage. In ng+ the strategy changes, but it is quite simple: Debla of the Lights. Viridiana is also available to heal you during this fight. When the 3 merge together, avoiding the massive laser should be your first priority since it does a lot of damage to you. You can parry some of their attacks, but since you will often be midair it is better to just try and avoid them.

Since there are 3 targets, getting into a position where you can hit multiple of them at once is a big help and will end the fight faster. This means that you always need to pay attention to your positioning, and I like to climb first and attack second. First of all, if you fall into the fire at the bottom of the screen, you're done for.

Blasphemous crisanta