Eating the garden?

my four month old pom loves playing outside in my backyard. the thing is she loves to chew on & eat twigs, dandelions, and sometimes gr. is this safe? are there any plants or flowers that are poisionous? we don't have any fertilizers on our lawn, i know that. and the pup has had all her shots (except rabies which she gets next month). it is just so hard to stop her! thanks!!