Spiders in a leaf pile! That makes so much sense. She was out there, investigating, and no doubt stuck her flat little nose right in the nest. The spiders responded in kind.
Glad she's feeling better and those bumps are going away. I don't know if you have black widows where you are -- we don't -- but a nest of those things could probably seriously hurt a small pup, couldn't they? Wolf spiders are often found around the lakes here and while I used to live in a cabin that was full of them (I know. Ewww. They liked my warm water bed.) Fortunately, no one ever got bit.