u/Melodic_Target_975

I hope someone here can help me with this.

I remember a book I loved so much i read in one day.

I read it between 1998 and 2007, it was a library book and lightly worn. There was no mention of modern technology so im guessing it was written prior to the mid 90s.

The main character is a woman who killed the wife of the man she was in love with (prior to the start of the story)

And now that he has a new woman in his life she is plotting to kill her has well.

The man has children (i vaguely remember two pre teens a boy and a girl)

The man has a vault in his home and at the end, to avoid getting caught she steps into the vault before it's to be scealed forever

Thanks in advance