I'm very sorry, JoZ. I've lost two to colic, so I have some idea of the pain you are going through. It's good you have her son. Eventually, you will look at him, see her in him and smile because of it. Right now, just grieve. If you're the crying kind, then don't try to hold it back because it does help.
I lost my lovely TB mare Secret to colic today. The worst thing is that her condition when I found her this morning indicates she was in pain for a good part of the night (abrasions on her hips and head, shavings and manure ground into her eyes).
Try not to think about that. We aren't/can't be with them 24/7 and all we can do is try to make them safe as possible.
Sorry for your loss. I'm glad you have a piece of her in her son.
Every post about a lost one makes me count my days with my old(er) guy. That's a good and bad thing, I guess.