Unless it was a firefly [aka lightning bug ] it is probably safe. All sorts of flies, moths , even bees + wasps can be eaten with no ill effects in most cases.
Yeah my dragon does that often (has eaten 3 yellow jackets just this summer which gave me a heart attack each time). I try to keep him close and stop him when I can and he doesn't go outside during firefly season though. Since it's so late in the season now I doubt what she ate will be harmful to her. Just keep an eye on her and watch for a dark black beard, vomiting, or other odd behavior. Based on what I've seen though it shouldn't be a problem.
It would be pretty clear that something is wrong. Her whole beard would go really dark black and she'd act lethargic or generally out of it. If it's something toxic it usually takes effect quickly so if she's acting OK now she's probably fine. That said, I find it comforting to carry a charcoal kit wherever I have my dragon. You can administer activated charcoal to help bind the toxins so they pass through without causing harm. At the very least it buys you time to get to a vet in a severe case. http://www.bug-de-lite.com/store/index.php?app=ecom&ns=prodshow&ref=Charcoal_Kit