A Hijacked Life — Scott Reeves

Perdida Solace is a lonely elderly woman living a life of isolation and despair. Her older sons are too busy with their own lives to have much of anything to do with her. And now her youngest son, her sole source of companionship despite their embittered relationship, is drifting away from her, his affections gravitating toward her ex-husband's new wife.

On the same day she is diagnosed with a terminal brain tumor, she finds a book of ancient magical spells, one of which will allow her to switch bodies with an enemy. She jumps at the chance, swapping bodies with her ex-husband's new wife. She only intends to stay in her hijacked life for a few days, long enough to experience a perfect moment with her son, Tom.

But she soon finds that a good life is not so easy to give up...