Photos look completely different when imported onto other devices

Hi all, I am trying to help my friend set up her Lightroom and have pretty much finished except for one problem, when she exports the photos, and downloads them on her phone and other devices, the colours are way off, contrast and exposure too. I am trying my hardest to fix it (from another country) as she is such a passionate photographer and this is very frustrating for the both of us! 

In my mind it was down to two things, 1. either her laptop screen isn't calibrated so it's causing the incorrect edits, or 2. it's caused by the colour space or colour profiles. I don't quite understand colour spaces and profiles just yet either.  

I thought as a test to see if it's an uncalibrated monitor, I asked her to export a untouched raw file from lightroom and onto her phone. I thought in theory this should look the same as on camera at least. But nope completely different. So Im guessing that leaves the cause to be colour profile/space related.

we have tried exporting them in both ProPhoto RGB and sRGB IEC61966-2.1. But nothing is making a difference. 

is there something i'm not doing? Any help would be greatly appreciated. 

for more context, raw files look the same on the laptop as on camera, until she exports them and they turn much much darker with less contrast. And those files are very large at 61 megapixels. (Thanks sony). Being exported as Jpeg, full size.