Let me first of all say that you've created a lot in a month. Well done!
I think your magical girl concept is very unique and I really like the way you linked it to Schrodinger's Cat. I don't know if the spinner when you die is biased or not, as with 4 deaths I was only revived once.
I was engaged in the gameplay, and exploring the world was fun. I liked the dialogue at the shop and the variety of characters which helped keep me interested in the story. I would suggest adding more frequent save points as I first died at the spider and did not find the nearby save point at the time, sending me back to the birth place. However, I kept my upgrades and the enemies did not respawn so it was easy to get back to where I was.
The other thing I would mention is that attacking in the air also locks your horizontal movement. I had done this in a game I made for a jam a while ago, and I didn't really see anything wrong with it until people pointed out it made jump attacking feel bad. I'd suggest changing it so that you can move horizontally whilst jump attacking, trust me it feels a lot better.
The graphics were great and I especially liked the character portraits. The animations are smooth and there is a lot of polish, just from the way the player moves to the different transitions you've included.
Both the sound effects and music were well chosen and suited the atmosphere of the game.
Nice game!