My journey to Linux was about 10 years in the making. Back in 2008, I had a laptop with Vista. I did not like Vista. I was not able to install Linux on my laptop. I paid a computer guy to install Linux on my laptop. It worked, but there was an issue was Wifi. Neither one of us could get Wifi to work consistently on my laptop running Linux. So, I switched to using a Mac.
I was a Mac user for about 10 years. My love affair with Mac ended because Apple started making iMacs and laptops with components (hard drive, memory, etc.) that were soldered into to machine and could not be easily upgraded or repaired. Also, Apple (and other computer manufacturers) made laptops so thin and light that there were over-heating issues. On Macs, the CPU would throttle down when it got too hot from being in such a tight space.
About a year ago, I bought a desktop from System76 that runs Linux Mint. So far, I like it very much.
As far as your friend's situation goes, I would guess that there is a good chance that Linux could be installed on her 10 year-old HP PC. However, I am inclined to not recommend this. Software availability for Linux is still not as common as it is for Windows or Mac. For example, not all printers are compatible with Linux because of driver issues.
I would recommend that she replace the hard drive on the HP PC with a solid-state drive, and install Windows 10 on it, if Windows 10 is compatible with the 10 year-old hardware. Otherwise, she should consider buying a new machine.