iCloud Mail Drop Re-loads every time

I successfully used iCloud Mail Drop to send a 350MB video to my sister yesterday attached to an e-mail. It worked well, and she could see it using her Windows machine on the other side of the world. (Latest MacMini with El Capitan.)

But the e-mail actually had a message in it, as well as the video link. And today, when I looked at the (saved) mail to my sister to remind myself what I had actually said in the message in order to continue the conversation, the video link started downloading the video again, even though it came from my computer and my account in the first place. And I couldn't stop it without switching Mail off completely.

So two questions:

Is there any way I can stop the video reloading on my computer, even though it's there already?

I had been hoping that having uploaded the video once, I could now send it to other people without uploading it again, but I can't find the link (as such). I was hoping that the link would be at the bottom of the mail I sent my sister, but if it re-loads every time I try to check, then it's useless.

Thanks for any help