Did she recently update graphic drivers or is she running out of space on the boot drive? Those are the first things i’d check.

If you hit ctrl-alt-F2 do you get a terminal login screen? You can type dmesg in that terminal to see the boot messages and see if an error is being thrown at login.

It could be a quirk of Acer indeed.

A propos, the advanced option of the Grub menu with Linux Mint will just show all the kernel boot options. For example, if you already have three or four older kernel versions you can choose among the older ones in case the new kernel would be causing problems. With a fresh install you would have only one kernel and its recovery boot option.