My cousin thinks she was a late wedding invite because her envelope came back to us

My cousin learned about our wedding because her invitation came back to us.

The envelope had been sitting in a box of returned mail at my parents' house for nearly three weeks. My mother found it when she went looking for extra RSVP cards.

The apartment number was wrong.

Before I could contact my cousin, her sister mentioned the wedding in a family group chat. My cousin replied, “I assume mine got lost somewhere.”

That sentence has been replaying in my head since Tuesday.

She was always invited. Her name has been on the guest list since the first draft. I addressed the envelope myself, copied an old address and missed one digit.

I sent her a private message immediately. I explained what happened, apologized and offered to hand-deliver a new invitation. She answered kindly but briefly: “No worries. I figured the list was tight.”

The list is tight, which makes the mistake look believable as a decision.

We have not been especially close in the last few years. We exchange birthday messages and see each other at holidays, but we do not call. Two other cousins were not invited because of capacity. From her perspective, exclusion would have made sense.

I want to make it clear that she was not an afterthought. I do not want to protest so much that my apology starts sounding like a defense prepared for court.

My fiancé says the cleanest answer is a phone call: acknowledge the mistake, say we want her there and send the invitation with the correct details. He thinks screenshots of the original guest list or the returned envelope would make the interaction stranger.

My mother wants me to photograph the postmark so my cousin knows the invitation was genuinely mailed weeks ago. She is worried the new invitation will look like a late addition after another guest declined.

That is exactly what I am worried about too.

The RSVP deadline is in eight days. My cousin may already have plans, and a formal invitation arriving now could feel like pressure to rearrange them in order to prove she believes me.

I could tell her that we would love to have her but understand completely if the timing no longer works. That is true. I also worry that emphasizing an easy refusal might sound as though I do not care whether she attends.

The error is small enough to explain in one sentence and meaningful enough that one sentence may not repair it.

Would you call, send a photograph of the returned envelope or simply mail the corrected invitation with a sincere note? How do you prove someone was always wanted without making them manage your guilt about an address mistake?