The husband of a woman I knew not so well through my church and children's school showed signs in his late 40's and soon was no longer able to work. Then the wife and I were co-workers, where I came to know her well and had great respect for the her for the burden she bore. All the members of this family have/had fine minds and have had good careers before some were diagnosed. As I understand it, presuming one parent is free of the disease gene, children of Huntington's parents have a 50/50 chance of inheriting the gene.

The disease was not diagnosed early in the husband, and as the grandmother referenced above, people assumed the irregularities in temperament was a psychological flaw. Years in nursing care followed.
After the husband died, their six children had the option of being tested for carrying the disease gene. That knowledge alone, if the test proves positive for the disease, is a heavy burden, affecting their present and future lives. AS I understand it, some were tested, others opted not to be tested.

One daughter, whose life had been erratic, including several marriages, told her mother that she believed that she had the disease. This was subsequently confirmed, and this woman deteriorated physically and spent her last years in a facility for "incurables", before dying.
A son, who had been a classmate of my daughter, was diagnosed at around age 40. He had a good mind and good job, and was married with one daughter. Soon he was not able to assist in his brother's deli, where one must multi-task during busy times.

The younger son, also married with one child, was convicted of child molestation, and sent to prison. It seems that his ability to resist certain urges was affected by Huntington's disease.

An older daughter also has the illness. She is unmarried, with o children.

Only two of the six children have escaped Huntington's - the eldest daughter, who is a college professor, and the youngest daughter, a physician. They each have two children, whom I presume have not been passed the disease gene.

Huntington's disease is a terrible scourge, both for the immediate victim and for the family members that may contract the disease.

May thoughts are for the young woman mentioned in the OP and for her family and all so afflicted.

the three surviving siblings have not been tested. Their dad told me that only one of the four had it. I hope that is right. The three siblings left are about the right age to show symptoms.

Arlo Guthrie is free of the disease. His father, Woody Guthrie, and his grandmother both died from it.