Here's one that reads warm without tipping into cringe:

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"For those who don't know, [Sister] and Elliot met at the climbing gym. Which makes sense — they're both the type to look at something hard and decide they're going up.

I've watched my sister become the bravest person I know. And Elliot, from the start, you made her laugh more and carried the quiet stuff alongside her. That's what told me you were the real thing.

So raise your glasses. To a lifetime of good routes, better company, and always having someone in your corner.

To [Sister] and Elliot."

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About 45 seconds spoken. Swap in her name wherever you see the bracket. If you want it shorter or a touch funnier, tell me her vibe and I'll trim it.