Palladium armor can be useful due to the Rapid Healing buff it provides.
Just like King Slime, if she cannot reach the player, she will teleport to them. The Gelatin Crystal can be found in the Underground Hallow among Crystal Shards growing on Pearlstone and Pink Ice blocks. Once used successfully, the item is consumed, and the boss is summoned. Queen Slime can be spawned by using a Gelatin Crystal in the Hallow (if used outside of the Hallow, nothing will happen and the item will not be consumed).