Doesn't seem like anyone can help you unfortunately.
The 52751 is one of the models that the forum does not have firmware for otherwise that would have been a suggestion to try and re-flash it.
Although Storage Options do not have the firmware shown on their website for this model, it might be worth asking just to see if they are prepared to provide you with an image.
It is impossible to guess at why the WiFi has failed... although if the tablet is otherwise working then you may want to consider trying a WIFI dongle - although Scroll tablets can be very fussy about compatibility and USB dongles.
A very long shot but it sound like you have little to lose..... Using a file explorer like
"E.S.file explorer" : have a root around to see if you can find any folder names beginning LOST.... if you do then try deleting them as these are created by the system when things go awry and the system tries to repair itself from information inside theses folders - usually files named with numbers.
You will do no harm by deleting these folders as the system will automatically recreate them as necessary and you just might get lucky if it is one of these number named files which is locking the WIFI up.
Good luck. Failing this then buy her an
"Excel III" with the new dual core Rockchip 1.6Ghz processor, 1Gb system RAM and 8Gb user RAM (LESS - subject to installed apps and firmware) Wi-Fi 802.11b/g/n and HDMI out.... not bad for a penny short of £110.00 and you may find it for less if you shop around.
Update Like here at
"Amazon"