The article implied that the spill was on the tray which means she was the one who probably spilled it. The tray would not be up unless she was using it.
It's not uncommon for the tray to be deployed and some fat toad sits down in the seat before you, causing the tray to move.
It wil be interesting to hear her spin on the situation.
Unless first class seats have changed in the past couple years the trays in first class are not in the seat in front - but fold into the arm rest between the two seats.
It's hard to say what happened - tho' I do know that I wouldn't want to sit in a wet mess.. in fact I held up people getting to their seats at Chili's on Sunday because there was soda (and a straw) in my seat. I had to ask two times for someone to give me a napkin or something... no way I was going to have dark colored soda all over the back of my cream colored skirt...