Help on changing game textures

I don’t play this game personally but I’m a pixel artist and my sister recently got the game. She loves her fashion so I told her I could help I retexture some of the outfits into something she wanted. I’m aware from my basic research that this is possible just by editing the sprite sheet, but I’m not sure on how to export the sprite sheet from the game, or even if there’s any easier applications or mods to do that. If anyone knows how I could do that it would be greatly appreciated.