I am so sorry for your loss. She looked like such a precious angel. How terrible for this to happen.
Being somewhat new to horses, I had to look up OLWS to see what the scare was about. When I found out, I admit I had to wonder why the stallion was bred knowing he was a carrier? Granted, the research I did said BOTH parents had to have the gene to produce (a chance of) a lethal white, but why take the risk if you know one parent has the gene?
I mean no disrespect. Please don't take it as such. I was just curious about it. My own mare just had her foal this month & I know how devastated I would be if something had happened. I, too, had to have the vet out (on a Sunday night of all times) because my mare didn't pass her placenta in a timely manner & I thank God everything worked out. I truly wish your little filly had survived.