That's extremely high. Could see that for a business deemed high risk (often based on its merchant category code) and/or with many chargebacks (customer disputes). 3%-4% average is more typical for many small businesses.

Assuming the $3 is right, the merchant acquirer (payment processor) is probably gouging her business. Sometimes it's not obvious either. It could be their base rate is competitive, but many of her transactions aren't qualifying for some reason and being charged more. Lots of reasons, including some types of cards, such as high rewards travel cards, Amex cards, etc.

Should shop around or, if sales are relatively low volume, use a pay-to-go option, such as Square, PayPal Here, etc. Most are around 3%. While not great, the hardware costs may be cheaper, especially if one can use their own devices, such as tablet, phone, etc. Many merchant acquirers bundle in the hardware cost into their monthly fee. Maybe that's where the excessively extra cost is coming from.

In short, she should shop around.