Jezebel called herself a prophetess and unrepentantly led Christians in Thyatira into license. Exactly who was she? I doubt there was a person in Thyatira actually named "Jezebel" at the time of the writing of the Apocalypse, but I do think there was an actual person in Thyatira around that time who was symbolically designated by the reference but was otherwise unnamed. What I feel quite certain about is that whoever was referred to by the name was not a "spirit" or a demon. It's not that I don't think that a demonic spirit could have been behind the activity mentioned, it's just that it's not at all discernible from the text if it is. It's better not to make such a claim.
Whoever the actual person referred to by Christ may have been, the qualities which make her a symbol for all who followed are that she was: 1) a woman, 2) who wanted those in the believing community around her to embrace practices foreign to true religion, and 3) who resisted all correction from legitimate spiritual leadership. Furthermore, this self-appointed authority was associated with teaching the "deep things of Satan." Christians never need delve deeper into the things of Satan than realizing he's on the prowl seeking someone to devour. Learning his secrets is not the means of overcoming him, rather getting deeper into the things clearly, openly revealed in Christ is.
My experience over the last 30 years leads me to doubt any claim to "deep things" from contemporary prophetic figures, so when I hear the phrase used by teachers today, my mind translates it into: "reading into the text something completely alien to it". I do not doubt the Jezebel referenced by John the Revelator would have foisted her teaching in a similar vein. In fact, since I see these letters as prophetically representative and therefore in force for types of the local church as it exists in various places at various times, I would expect that at any given time some local church would be dealing with such a figure in their midst. If and when that happens, even though the false prophetess' name may not, her way most certainly should ring a Jezebel.