I had the same feeling, Smrobs, that's what I've always done with my dogs, but my vet, the breeder and my sister-in-law told me to go ahead and worm her, because babies don't have as much resistance to parasites as adults do. I obviously had the wrong info about not changing the wormers often. I should have read more about it, but I've never had problems with parasites with my dogs, even though they go to parks, dog shows, pretty much everywhere. I've been stressing over her diet, her hoof trimming, training, companionship, etc.
And Waresbear, your filly had been neglected, with a horse that had not have regular care I wouldn't have been surprised, but when you think you are doing everything you need to and find out that you're an idiot, I can't explain how that feels. I'm not good at many things, but I'm (usually) a good mom to my fuzzy kids. I love them, I understand them and I pride myself on being a great mom.
Thank a lot guys! You've been very helpful!