Go your way and let her go her way. She is your friend but you can’t marry her because she sleeps with other men and you can’t stand that. Fair enough. Tell her to please not kill herself; you are not the only engineer in the world. God bless you.

But be aware that you are too hard on people and you may never find what you so strongly claim to be looking for. In this 21st century o, pesin must sleep with different people. If you like go to the Vatican to look for your own spouse. Most people still have the attitude that fidelity/infidelity means something, but it is no longer so. Ask. Those times have passed.