like others have said in this thread, she sounds like she is having a mental breakdown, or a life crisis of some sort and is lashing out at you. based on what she had written in her email to you it sounds like in her mind, the life you live outside of the hobby-ing is the kind of ideal life she wants or had wanted at some point in time. when i read what she wrote it seems as if she has other issues, it seems she harbours resentment for a person able to live with a secret such as hobby-ing or even jealously of the fact that you have a family to go to after you are done with her.
i wouldn't take her threat seriously yet, she has given you a deadline. you can run out some time see if she gets more desperate and emails you more. she hasn't physically done anything more than email you yet (like call, text, or show up at your door). if things escalate i would suggest seeking possible legal advice.
at the moment, what she has written seems like a desperate cry for help, a very desperate cry. may be she targetted you because you treated her well, she believes you are well off enough to pay up, she believes she can get away with it, or she hopes you can talk her out of whatever pushed her to do this.
if you know shit is about to hit the fan, get ready for it, prep your wife for the news. trying to make this a discreet matter may require action on your part at rooting out what and why she is doing this to you, why you are her target and why she believes your money shall set her free.
i think there are more underlining issues than money with her. it feels like a emotional problem coupled with regrets and resentment.
i wish you the best of luck in dealing with your situation.
