"She wanted to do great things, but all that vanished."
Translation:Elle voulait faire de grandes choses, mais tout cela s'est évanoui.
Technically "disparaître" is really precise and means "can't be seen anymore". So normally a chair, a car, a light, a smile, a feeling of happiness in eyes can "disparaître" because you can see them if they exist (even for more abstract things like the happiness in eyes). Here you can't see that she wanted to do great things, it's just a state of mind without any physical appearance so you shouldn't use it.
But, to be fair, it's really really precise, if you speak to french people, they will say and understand "disparaître" in this case without any problem or hesitation.
In French, the partitive article 'des' becomes 'de' before an adjective. This happens when the adjective precedes the noun.
So 'des grandes choses' becomes 'de grandes choses'.
I am guessing this has to do with the difference between something that happened once, discretely, and is already over, and something that 'used to be' or was going on. She used to want to, but then... see https://languagecenter.cla.umn.edu/lc/FrenchSite1022/FirstVERBS.html