I would call the vets to ask their opinion. Especially because it is sharp and pointy you want to make sure there's not a chance of it cutting anything as it goes through her system. In the mean time just keep a eye on her, and if she starts acting differently or gives any cause for concern I would bring her straight to the vets. Also keep an eye on her poop to see if you can tell if/when it passes.
You said that the plastic was pointy and sharp...what did it belong to? (We need that information so that we can tell you if it's poisonous or not.) You mentioned that she isn't acting any different... then she may be alright. You may want to look when she goes to the bathroom to see if it passed through her system, just to be safe. And if it's that small, then there shouldn't be a problem . If you do notice anything different though, I would definitely contact your dog's vet and bring her for a quick check. Good luck!:thumbsup: