I believe that she has a PSR-E443, which does not have direct USB audio output. So, she'll need an analog-audio-to-digital-USB adaptor. There are plenty of these available for a wide variety of prices. I use a very basic unit from a company called Behringer which cost about $30 US. It's straightforward -- just hook the analog audio input of the device to the keyboard's headphone output (this may require an adaptor plug). Then, hook the USB output of the device to a USB port on your computer. I've used it on Windows 7 and Windows 10 and did not need to install any special drivers. But, yes, you will need a computer program, called a digital audio workstation (or DAW) that can get the information from the USB port, interpret it as music, and record it digitally on your computer. The DAW can then save the music on your computer and even convert it to WAV or MP3 files that can be stored on a flash drive, CD-ROM, or other media for playing the music on stereos or other equipment away from the computer. Or, the files can be just transferred to a phone or other portable digital audio player like any other music file.
As Fantomas said, you can use Audacity software. It can be downloaded to your computer for free and is quite powerful. I have been using it quite a bit to record multi-track recordings from my PSR-E433. It can convert recordings to WAV, but if you want to convert recordings to MP3, you have to download a separate companion program with Audacity, which is also free. I believe that the instructions for Audacity on the web also give you instructions on how to download this MP3 program, curiously called "LAME."
There are also other considerations, such as making sure your computer is set to record in stereo instead of mono, adjusting levels to reduce or eliminate noise, and how to listen to what you've already recorded if you want to "overdub" or do multi-track recording, but I don't want to make this post too long, so we can tackle those subjects later.