My daughter’s name is Alexandria. Though it wasn’t last minute and I love the name, like you, I naively thought people wouldn’t shorten it.

I do my best to correct people but it’s family that’s the hardest. Everyone wants to call her Alex or Allie. They say “Alexandria’s jus too long” ugh it’s quite frustrating. If I wanted to name her Alex or Allie I would’ve. But nope, it’s Alexandria goddammit!

So yes, as other people said if you won’t change it and truly love Madeline then reinforce it.

As for your concerns with changing it, I think you might be overthinking it or worrying too much. No one can say wether you’d regret it or not but I don’t think your child will be against it. Perhaps she’d tease you, or make fun of some aspect of it but I think it’d be lighthearted .