Is suicide a wrong choice for a person with terminal illness?

In early November 2014, Brittany Maynard ended her life by choice. She was suffering from terminal brain cancer and probably wouldn't have survived till 2015. The story was highly publicized and elicited a lot of reactions. Some people asserted that Ms. Maynard had no right to end her life, even though she'd spent a long time honestly deliberating on it and decided she did not want her death to be long and painful. What is the basis for the moral opposition to this kind of suicide? Her choice seems rational to me, but others clearly oppose it. Is their opposition purely religious in nature? Is it based on Kant's duty ethics? Is there any validity to such opposition, or should the right to "death with dignity" be adopted in every state, rather than in the five in which it is currently legal?