Does she get the Windows 10 logon screen and desktop?
There are some Windows 10 updates that take AGES to download and install (some are a complete replacement of Windows) so maybe leave it on over night (plugged in to the mains supply) to see if that fixes it.
If you really cant get it to Windows then you can download a copy of Windows 10 (legally) from here and then put the image on a USB stick (it wont fit on a single layer DVD) and then boot the laptop from the USB stick and reinstall Windows.
https://www.microsoft.com/en-gb/software-download/windows10
See if you can then do an install where it reinstall Windows but does NOT overwrite your personal files.
Also you MAY be able to download a Windows 10 image from the company who built the laptop (HP, Lenovo etc) on their Support page. This will have all the drivers and programs that came with laptop already installed so may be better than a clean install of Windows 10.