MacBook Pro Mid-2012 starts but does not respond anymore
One thing that does happen at times with MacBooks of this kind (own one myself and had it happen to me) is that batteries can over time "inflate" and slowly but surely push themselves against something — in this case it would be weird if the something was the mainboard since it's not located under the battery but rather beneath it). But maybe you could take it apart and see if the battery looks odd or even a little blown-up and ask your friend if she ever replaced it before..?

Some basic steps to perform:


To rule out possible battery faults, you could take the battery out,
then try turning it on with the power cable attached
Give the obvious "mac-things" a try such as SMC reset, PRAM/NVRAM
reset etc.
Take out the SSD and attach it to another computer to see if you can
start it up from there