My wife doesn't flush the toilet?

Recently, My wife has not been in the habit of flushing the toilet after she uses it. The first 2 times she did that, i thought she forgot, but its been going on constantly now. I even put a "FLUSH TOILET HONEY" sign on the door so before she leaves, she will remember to flush it. But still to now avail. It leaves a very deadly smell in the whole house when i get home because she doesnt even close the frikkin door.

I asked why she doesn't flush and she replies with the usual "I forgot". And i also one time saw her poop the colour of green, which made me almost throw up. How do i make her get into the habit of flushing the toilet with out being too harsh on her? We are also thinking about having children so her bad habit wont set a good example.