if ur mother in-law 2b,is segxwally tied 2u...what wud u do? especially when you love her daughter more than anything in this world and wouldn't want 2 hurt her....hmm
If you tell ur friend,she will take it on u as an enemy,and who knows what she would b up 2. Also if u call her and talk sense into her,she could eventually turn somewhere else and still also cheat and destroy d precious heart of ur friend.