AITA for replying by text to my grandmother's long letter instead of writing one back?
AITAI sent Grandma a photo of my graduation certificate and wrote, "Thank you for the lovely letter. Really kind of you."
She had written two pages about finishing her own course decades ago, asked about my final project and told me what she hoped I'd enjoy next. I read all of it. I liked it enough to put it in a drawer with other things I wanted to keep.
A week later Mum asked whether I'd replied. I showed her the text. She said Grandma had meant to start a correspondence, not just send a congratulations card.
Grandma uses messages regularly. I assumed a quick reply with the certificate photo would show that her letter reached me and mattered. I didn't answer her question about the project because I'd meant to write more when I had time.
Mum says I should send a proper letter now. I said a text isn't automatically less proper just because it isn't on paper. She replied that I was arguing about the envelope to avoid noticing how little I'd said.
I don't want every letter to create a duty to answer in the same format. But mine was mostly thanks, and hers was a conversation I hadn't really joined. AITA for replying by text?