I think your stated intentions are good, but all this smearing you’re doing of her 1) doesn’t really make this a “clean” ethical question and 2) doesn’t really make you look all that good yourself. Better to ask the question and not throw in things like she’s a debtor, a drunk, a drunk driver, a manipulative gold-digger…
Anyway, if your intention really is to sort this issue out, here are a few thoughts;
First, separate the legal issues from the ethical ones. Theft is a legal issue, and to me “market research” of the clients she’s working for doesn’t sound like it would fall within the legal definition of theft - accessing data, or even making copies of it provided it is within the scope of her consultation, is probably legal. It depends on the state she’s in and what she is “researching” though - it may very well be that the kind of information she is accessing or copying represents a trade secret or similar protected data that would fall under a theft statute. There are other criminal laws that she might be violating as well, such as unauthorized use of a computer system, which she might violate simply by accessing a database that she was not permitted to access. And in addition to criminal law, there would be civil violations as well that could put her at risk of a lawsuit. Certainly giving or selling this data to third parties would represent another layer of liability, potentially criminal and civil.
As to the ethics of it, that also somewhat depends on the circumstances; if she’s pulling information that she’s not authorized to, or that is not within the scope of her consultancy, then I would say no - this is not ethical behavior. If however she is simply learning about a kind of business by consulting with them, that seems perfectly fine.
For instance, let’s say she’s hired by Company X that makes widgets at price $Y to do an analysis of their sales and give guidance on future sales. She works for them for a few months and finds that selling widgets at price $Y is not working all that well, and that though their margin might be less at a lower price, the increase in volume would more than make up for it. So long as she does her job and presents her findings accurately, she’s done her job and she’s learned something. That something that she’s learned is now her knowledge as well as that of the employer - there’s nothing the employer can do to make her unlearn that information. So if she decides she wants to go in to business selling widgets and price them at $Y-1, there’s nothing unethical about that. And if the employer wants to prevent her from doing that, they should protect themselves with an NDA or noncompete agreement that reasonably limits her ability to take her newly acquired industry knowledge to start a competing business.
Where it gets a little more complicated is when she gets her next consulting gig with Company Z, which is a direct competitor. Of course that’s why she got hired; her experience and knowledge of the industry. And she can use that in an ethical way, by communicating her knowledge without violating the trust of her previous employer. Where she would cross the line is in divulging anything specific, such as the specific sales volume, costs, prices, history, etc of the previous employer, or worse actually handing over any documents. That would be unethical.
The test for determining that seems pretty straight forward to me - a variant of the universal imperative; if your future employer found out she did what she did with her previous employer, and knew that she was likely to do it again with them, would they hire her? Simple; if she provided thoughtful analysis by understanding the clients needs and interests without revealing other clients’ information and damaging them in that process, that would be ethical and nobody would have anything to hold against her except that as a consultant, she’s learning a lot about an industry. If future employers found that she had used previous clients’ information to damage them after she left, by helping competitors or helping herself, then that would be unethical and she would not get the job.
Finally, I would say that there is often a solution to questions of ethics; transparency. If she’s honest and discloses that she intends to access certain information from clients and use that information for her own market research, then as long as she tells her employer that, there’s not a problem.