Bluntly, her work are taking the ****. The problem is, she is allowing them to do so. Surely seeing people move on and up, earning more than her etc is a huge red flag and shows how little they value her?
I am guilty of booting up the laptop and getting some work done, but that is only if it aids me in getting a head start the following week. I also may take a call and help with an urgent issue. But this has become the norm for her, that is unacceptable.
The company are allowing this to happen and getting free labour, this is probably why she is not moving on - she is doing the work of several people 24/7. Why would they move her on if she is content to continue to keep doing this? She is a victim of her own success.
She needs to take a breath, step back and review the situation. Then book a meeting to discuss her concerns and express this cannot continue - she either stops offering the level of support she is giving or she is suitably financially reconciled.
But NOTHING will change unless she speaks up.