Still scraping my jaw off the floor.
You were homeless and someone took you in and got you a job, and after you cause her "drama" you don't apologize?! Your emails were *incredibly* rude.
You are so wrong in so many ways.
1) Your employer is calculating correctly. Every employer I've ever had used this method.
2) Yes, your employer can fire you. http://www.calaborlaw.com/can-my-boss-fire-me-at-any-time-for-any-reason-what-is-%e2%80%9cat-will%e2%80%9d/
3) The only one making your work place unpleasant is YOU.
Honestly, were I in your shoes, even if I *thought* I were right, I would have bit my tongue after "Jennifer's" first reply.