im assuming her concern is if the shidduch doesnt work, which may lead to awkwardness between you two?
That would be a more rational fear, but still a selfish consideration. If that were her reson, I would tell her to be mature about it; if it’s appropriate, redt the shidduch, and if it doesn’t work out, keep your frienship anyhow.
It’s also possible that the sibling doesn’t think it’s an appropriate shidduch and is using awkwardness as a cover, in order not to insult her friend.