Is it safe to eat green onion slime?
Normally, people associate slime with "inedible" because some bacterial colonies can build up slime on spoiled food. But there are plants which naturally produce slime, and it is as edible as any other part of the same plant. Slimes are most common in algae, but I have also seen them in other plants such as hyacinth greens, and scallions have it too, although in normally not that much. But if you mash a "dry" scallion or the greens of a typical yellow onion, they still feel slimy, while other alliums become slimy on cooking, for example leeks. 

Physically, slime is just a special kind of gel. As long as it is not of bacterial origin, it is not a sign of spoilage, and it is highly improbable that a living green plant without signs of sickness will be full of colonies of spoilage bacteria. So, I would declare it good to eat.