Enflamed Billionaire: Demented Pleasure by Evelyn Love

Shaun gets back into Oscar’s life with the pretext that she is dying. She plans with her new boyfriend to kidnap her own daughter and get the ransom from her husband.
In the middle of the kidnap, she realizes her boyfriend does not really give a f**k about her, and the funds she wants to use and travel the world with him might end up being his alone.
So, she exposes their plans and runs away. Her boyfriend is cut while she returns to Oscar’s house to find her ex-husband and his lover making love. She has a gun and the intention to commit murder.