The 21-year-old singer's grandfather has confirmed she has the auto-immune disease, following rumours that she was battling the condition "a couple of years ago".
But he insists she is learning to cope with the illness, reported Radar online.
"She is in treatment. She is getting along pretty good," Ricardo Gomez said.
Ricardo hinted that the former 'Wizards of Waverly Place' actress turned popstar could be close to giving up her singing career.
"She was saying she doesn't want to sing any more, she just wants to be an actress... But she's going to combine it, it looks like," he said.