I would call poison control first thing. They have a wealth of correct knowledge at their finger tips and will know just what to do. That's who doctors/ERs call when they don't know an answer.
Ultimately, though, it will likely pass. If it got lodged in her intestines or something, she would let you know that she was in pain. I remember swallowing a nickel, and it came out in a day or so. Any effect she has from ingesting the coin will likely be less damaging than surgery, which would probably be the only other option. You might watch her stools so that you know that it does come out. My son, at around 14 months, swallowed an open staple. My gut said it would be fine, and I fed him some cookies (something he would be sure to eat) to cushion it. Then I called a nurse hotline, and the nurse freaked out and said to get him to the hospital ASAP. So I took him in, and they fooled around for a few hours, then sent us to a children's hospital an hour away, where they anesthetized him and went down into his stomach/intestines with an endoscope, and found that it was long gone. "Don't bother looking for it in his diaper" they said, "as you'll never find it". Well, I did look, and it came out 25 hours after it went in, having damaged nothing (but the endoscope scraped up his trachea, and anesthesia is always a risk) and $2000 poorer for us (starving students at the time). I decided then that I would follow my gut.
There have been observational studies (information evaluated after the incidence) of people (probably children) who swallowed razor blades (I kid you not). The body formed a mucus around the razor blades, protecting the body. The body is amazing. I don't know why they say kids must be at least 3 to play with "small parts", as my three-year-old still puts things in his mouth, too.