It is unfortunate that you did not have an attorney to draft a written owners (shareholder, operating, or partnership) agreement. Regardless, it appears you have an oral agreement to form a partnership or joint venture. That means you both of contractual and fiduciary obligations.
The best way is to get a signed agreement, assuming this business venture should be saved (which I question based on the new demands and the account threat) You say she is "wiping" the bank account. How much of that are your funds? Aren't you both on the account? What basis would allow her to remove all funds from the venture account.
Ultimately, you need to get what you should have had at the outset, namely an attorney. The attorney can be available to attempt to resolve this dispute and if that is not possible then consider legal options for breach of contract and other claims. Good luck.
This answer is for informational purposes only and is not legal advice regarding your question and does not establish an attorney-client relationship.
The gist of my answer appears in a comment below attorney Murillo's answer. I want to add that lawyers are trained to resolve disputes and there are often a number of creative ways to settle differences and preserve business relationships. One thing to consider in preparation for such discussions with a lawyer is the origin of your dispute with your partner. (Because fact about the origin of your business relationship and the dispute likely contain confidential information, I strongly recommend that you *not* post such details here or in any public forum. I am just offering a suggestion that may be helpful as you prepare to consult with a lawyer about your issur.
I am answering this question and other questions related to the law, here or at other Web sites or other Internet forums, solely to provide general information. None of this information is legal advice. My answering this question and your or any person's reading my answer or any information to which my answer may refer or link does *NOT* create any attorney-client relationship between me and you, or between me and any other person. You should not disclose any private or confidential information publicly, whether on the Internet or otherwise, and you should consult with a lawyer licensed to practice in your state to obtain customized legal advice for your unique situation.