There is nothing wrong with feeding frozen if she takes it. If that is what you'd like to feed then you should give it a shot. Heat it up well, use tongs/hemostats and "walk" the mouse around like its alive a short distance in front of her face. For one of my snakes that I switched to f/t I had to heat the mouses head to a higher temperature than its body for the first few feedings. Its theorized that this more naturally mimics the heat signature of a mouse. Whether it is true or not I don't know, all I know is it worked for me. I'm unsure what you meant byPlease don't feed your snake string.If she doesn't eat it like that maybe attaching a string to the tail will help?
Also you should be prepared to feed live if she wont adapt to frozen/thawed. I've always been able to switch them but I've heard there are some that just wont do it.