Probably not either ethically or legally.  A sponsor list is a donor list and the Association of Fundraising Professionals, in its Code of Ethics, makes clear that its members shall adhere to the principle that all donor and prospect information created by, or on behalf of, an organization is the property of that organization and shall not be utilized except on behalf of that organization.  (www.afpnet.org)  Unless you authorized the woman to take and use of this information, it seems to be a clear breach of ethics to take it and use it elsewhere.

Perhaps more importantly, because it is legally enforceable, the Uniform Trade Secrets Act, adopted in some form in 43 states and the District of Columbia, creates liability for misappropriating a trade secret.  It defines a trade secret to include information that derives independent economic value from not being known, or readily ascertainable by proper means, by others who can obtain economic value by its use, and which is subject to reasonable efforts to retain its secrecy.  If you have tried to protect the information, and you are the litigious type, you may be able to enjoin its use, collect damages, and get paid your attorneys’ fees in the process.  Others have done so.  (See Nonprofit Issues®, 3/16/07.)  You may also find that a discussion, and perhaps the threat of suit, will get the woman and her new organization to stop using your information.

2024 UPDATE

More recently, a federal District Court in New York has thrown out trade secret claims against a former CEO of a school who used student, faculty and donor lists in starting a new school.  See Nonprofit Issues, Vol.XXXIV, No.1.