"Over the years of interacting with all of the children there had never been any mention of illness," Vanderpump explained. "[Their father] Mohamed had always said they were fine, but that is their prerogative as parents, whatever medical issues or information they choose to divulge. I obviously interpreted that as they were not infected by this insidious disease, and as it is not contagious, I understood them to be healthy."
However, the 55-year-old reality star admitted that she "had no reason to question their well-being," and added, "I love and adore all three of them, for sure."
Foster only recently revealed that two of her three children suffer from the illness. Her 20-year-old daughter, Gigi Hadid, is the only one who is not afflicted.
Foster's battle with Lyme disease has been one of the subjects of RHOBH's sixth season, and Vanderpump recently called into question whether or not the 52-year-old former model was even afflicted with the illness.
On Wednesday, Foster shared a photo of herself lying next to her 19-year-old daughter, Bella, who appeared to be undergoing treatment for Lyme disease.
"Watching my brave babies suffer in silence in order to support me in my journey has struck the deepest core of hopelessness inside of me," Foster wrote in the caption. "It is because of them that I continue to fight relentlessly."