Oh, honey! I'm so sorry. . .
I wish I had seen this thread yesterday, but she went so fast, there probably wasn't anything you could have done to help her. . .
still sorry you had to face it alone.
If she was in a community with other fish, I would recommend doing a water change, and keep a close eye on the others for any signs of the same issue with them. Hopefully this was a random one-time thing, but if not, we have an area of the forum dedicated to
helping with illness. If you see ANY signs of this 'white spot' on your other fish, please fill in the Diagnosis form you will find there, and post for help.
*hugs* I'm sad for your loss. . .