Kelly Addams 
The Cult [EPUB ebook] 

Twins are always close, so when Sara’s twin sister disappears into a secretive cult led by enigmatic Guru Ashtara, she is determined to set up a rescue, her twin has clearly been kidnapped or brain washed. But when she manages to get inside the cults headquarters she witnesses that her sister has become a priestess, a respected leader herself… maybe she doesn’t want to be rescued.