If you're an at-will employee, you can be fired for many reasons, however, there is always the possability that the disclosed reason is a pretext for an improper one, such as ageism. If so, you should consult with an employment attorney to determine your rights.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.
I am not licensed to practice law in Illinois so the following should not be taken as legal advice but simply as information intended to be helpful. If you need legal advice, please consult a lawyer who holds Illinois licensure.
There are many things which I would want to know to be able to answer the question definitively. If you hold at-will employment, meaning no contract and no employment manual which could reasonably be construed as a contract, they can let you go for any reason they want, except for legally impermissible reasons like race, religion, national origin, gender, and so forth.
Can companies, generally speaking, dismiss the highest paid workers in order to save money? The answer is YES. The rule may be different in employment where the business is unionized and there is a collective bargaining agreement. However, you do not mention whether your company is unionized, so I assume it's not. So, YES, chances are they can do that.
Of course, I would have to see it in the suit brought by her husband to answer this fully. However, as a general rule money in a joint checking account is owned by both parties to the account. Furthermore, it sounds as if the money, and possibly the debt, or marital, in which case the divorce judge would sort out who owes who.
Your situation involves important and complicated matters of law and fact. I urge you to consult with a lawyer on this matter.