Do you believe that TeLinde and Guy had the right to obtain a sample from her cervix to use in their research ?

Rebecca Skloot's book about Henrietta Lacks and her immortality has played an important role in highlighting the ethical issues involved in "informed consent"—or the lack thereof—in earlier eras.
Taking a tissue sample in order to arrive at a diagnosis on a living patient is part of treatment. Analyzing it following a patient's death could be part of an autopsy, which only sometimes requires the family's consent.
If the researchers were sure their actions were both legal and ethical, it is difficult to imagine why they and the JHU (as a research institution) kept the action secret for decades. When they started reproducing and selling cells at astronomical rates, it would seem like common decency to at least inform the family—not to mention make financial reparations.
In matters of science, issues of legality and ethics are often separate matters. Because of a long history of abuse (especially involving poor and minority communities) within the field of scientific research, regulations have been put in place. One has only to consider the gross mistreatment of African Americans in the Tuskegee syphilis study to understand the need to discuss ethics in the scientific community.

Henrietta Lacks was diagnosed with cervical cancer. One of the doctors, Dr. TeLinde, obtained a sample of her cervical tissue which he shared with Dr. Gey, a cancer researcher at Johns Hopkins Hospital. Lacks's cells, later referred to as HeLa cells, were found to be more durable than most cell samples. A faster rate of reproduction was also observed in her cells. These qualities allowed for more extensive research without damaging the cells.
In order to form an opinion on whether or not Dr. TeLinde and Dr. Gey had the right to obtain and use her tissue sample for research, it is important to consider the circumstances at the time the sample was taken. Lacks's tissue sample was removed in 1951. At that time, there was no protocol on obtaining consent. Since there was no protocol, it would have been difficult to show evidence of any violation of patient rights. The positive benefits received from the research conducted on her "immortal" cells could be seen as outweighing the negative.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5072843/