Wow, that was rude. You can download the installer to a USB pen from another computer and install it from there.
Tell your grandma it’s the only option and that there’s nothing else; say it’s the “upgraded version”. She’ll get used to it, it’s not that different. I did exactly the same thing with my parents and they got used to it in about a day.
Internet Explorer is heavily integrated into the OS, so troubleshooting it can be a real headache. In a lot of cases it’s easier to simply reinstall the OS. In your case, it sounds like installing an alternative browser is the easiest and smartest thing to do.
Good luck.