Can't get into recovery mode on boot

I'm trying to fix a remote laptop to which I do not have any physical access. The person who uses this laptop has no technical knowledge so she can only do what I tell her to do over the phone.

There is a problem with one or two volumes (sda7 and sda8) so when she boots the laptop, she's got a message "Use Ctrl+D to continue or Press Enter to get into recovery mode" or something like that. Ctrl+D does not do anything. Pressing Enter takes her into root prompt. So I was trying to run fsck from there but it fails with a message like "fsck error while loading: cannot open shared library" or something (Sorry I do not see these messages and have to rely on what is read over phone but someone who doesn't speak English).

I tried to navigate her into Recovery Mode through the GRUB menu but running the kernel in recovery mode fails for some reason. She can see the Recovery Mode but the options are not active.

So I am a bit lost here. I have not got any idea what try next. Because of the COVID (and she's elderly) there no way for her to ask someone to come and try to fix it for her or even to buy a new laptop (someone will have to set it up for her).

So I wonder if there is any other way to run fsck on the system (LiveCD is also out of question, unfortunately)?

She's got dual Windows 7/Ubuntu 16.04 boot but she's never used Windows before. Also, there's no TeamViewer on Windows so it's difficult for me to set it up for her.

In any case, any help is really appreciated.