I would not lie, I think that shows more disrespect.
You need not go in to details, you simply ask her to respect your choices.

i probably would in that instance.

I did at one time. Sometimes the little white lie is ok. You made your grandmother feel better.

I think there are occasions when it is ethical to tell a lie. I have lied to avoid hurting people. I have also lied to mean, aggressive people, to get along and keep the peace. You know, a situation where a boss or the boss's favorite pet, demands information about my opinions, lifestyle and that sort of thing. (It goes w/o saying that I have to keep the paychecks coming until I can leave that toxic workplace.) Survival lies and kindness lies. If telling the truth will cause problems you can't solve, then you must use your judgment.

I don't talk about treligion with my parents and they don't know how I really feel. In their mind they see me as a non practicing catholic who doesn't go to church. And they bug me about it sometimes, but for the most part they let it be. If I told them my true beliefs as a non believer, they would feel like failures as parents, and based on their own religious beliefs would have to accept that I am doomed for some eternal punishment. I see know reason to burden them with that. I let them believe what they want to believe. They can believe in their religious myths. And they can believe that I still hold onto a part of that. It doesn't bother me or affect me.

When i was a Jehovah's Witness, I thought nothing was more important than truth. Nowadays I'm convinced that was wrong and kindness should be the priority.

Some people have zero tolerance for lying, or so they say. I think that you did the right thing. No harm.