Does she not receive notifications from Twitter? Thus proving there is no shadowbanning?
The definition of "shadowbanning" entails giving the shadowbanned user the false impression that his or her contributions to the site are being published.
Then it sounds like shadowbanning can (in some cases) be more a mental condition than some kind of a cenzorship.
Otherwise, there's a question: why could user publish a site that they think is shadowbanning them?