You're in a tough situation, obviously, but I find the choice to be a simple one: your job or (potentially) your freedom. If you follow your employer's instructions to lie and you're aware of it, you hang yourself on the same hook as your employer - and you could end up with the same consequences if caught.
In the long run, conviction of crime is a worse consequence than losing your job for being honest. You are taking a risk even working at a place like you describe, and I'd personally find it hard to feel any true job security when that house of cards could tumble at any moment. Your situation touches more on criminal law than employment law I'm afraid. Good luck, and be careful!
Lying to banks (misrepresenting assets, buyers, etc) can get you into more trouble than losing your job. If your boss doesn't understand that she is asking you to commit unethical and potentially illegal acts, you may want to start looking for another job where the business is managed properly and ethically. Chances are good that you are not the only one at the office who is under pressure to "stretch the truth" and your whole office may be facing an investigation in the future. Again, you may want to start looking for another position in the event that the whole business is taken down by these shady practices like misrepresented properties or buyers.
Your e-mail provides a written record/time stamp of when you put your boss on notice that you "will not lie to push our deals through." That may provide a wake up call for the boss. It may also later be evidence that at least one employee wasn't willing to lie to the bank officers.
This is a general comment to your Avvo posting and is not meant to constitute legal opinion or advice. This informational posting does not establish an attorney-client relationship in this matter. Please do not distribute this information to others as legal advice. If you think you need legal advice or legal representation for this question or matter, you should consult a licensed attorney in your jurisdiction.