My first springer used to steal all the cats toys, this one steals my little dogs toys. I think springers are just greedy and selfish!
Seriously thou, don't play with her if shes snapping, once she gets like that stop play and yelp/ ouchy sound at her. It re-enforces the way mum and litter mates tell her enough is enough. When my two are fighting (playfully) over a toy, I take it away and don't let either have it, they look at me as if I'm odd, but then go off and get seperate toys each (but then 5 mins later the springer is then usually trying to steal that!)