Giant UGH!!
NO culture on this planet allow brother-sister marriage...well, any SANE culture.
And, from what you've reported about her...she's also a LIAR.
Quelle suprise!
In many countries it is your duty to lie, cheat, and deceive those not aligned with your views. That is what blue states are doing right now. New Your, Massachusetts, New Jersey, Illinois, Michigan, Arizona, Colorado, New Mexico, California. They are rogue terrorist states where "anything is ethical as long as it advances the revolution". (Karl Marx)