For my arena I used asphalt for probably a thousand blocks and put ramps at the sides. I also put lots of sunflowers to give me even more speed. I did not put any platforms above the arena I just landed back at the bottom and kept dodging.

For me I used the Empress of Light expert mode drop for mobility I used bad wings too but if you can go for fishron wings. Thats for my mobility For dodging I used Master Ninja gear a black belt and cthulu's brain which helped once during the fight so it helps but if you dont have a crimson you can still get by. I lastly used the celestial emblem. those are the accessories that helped. And for armor use hallowed armor the set bonus is insanely helpful. For me I fought her as a summoner but used melee throwing items but you can do whatever.

On youtube I found lots of great dodging techniques and they helped a lot I mainly just would circle a lot though it dodges quite a lot of attacks. Dodging is really hard in this fight but as long as you just keep fighting her you will get there it took me about 45 attempts Im pretty sure so it does take time and just wait you got this. If you want to see me fight the boss it is on my profile if you want help on knowing how to dodge.