Although I generally agree with you, she said she regretted the attempt:

“I felt so guilty that I had put my family through such pain. I felt horrible.”

Even if we were to agree with such a right, you would have a duty about how you do it to reduce trauma to others and society has a duty to make sure it is a rational choice. Also, even in a world where adults would have that right, but I doubt those under 18 would without special circumstances such as terminal illness.