I think you need to report that to the Better Business Bureau. Also, most states have a Consumer Protection or some such thing where you can file a complaint. That was definitely an overcharge in big proportions. You sound like you might be a little timid. Do you have someone who could help you? We're all in your corner and don't like to see soneone take advantage of you.
Also, you probably aren't the first person she has overcharged, so if you report it, at least it's on record.