2:20 But I have this against you, that you TOLERATE the woman JEZEBEL, who calls herself a prophetess and she teaches and leads my bondservants astray so that they a) commit acts of IMMORALITY and b) eat things sacrificed to idols.

But I have this against you, that you TOLERATE the woman JEZEBEL,

There may or may not have been a real Jezebel in the Thyatira church. But the name clearly points to the one that the Jews knew about in the Old Testament. (1 Kings 16:31-33, 1 Kings 19:1-3, 1 Kings 21:1-16, 2 Kings 9:30-37).

The Old Testament Jezebel was difficult on King Ahab and caused terrible trouble for true prophets like Elijah.

who calls herself a prophetess and she teaches

It is one thing to have a false prophet in the midst of a congregation but it is even worse when that false prophet is permitted to teach. Perhaps that is why Paul clearly tells Timothy that as a matter of principle, women are not to teach (1 Timothy 2:11-15). How many cults today are being lead or were started by a woman?

and leads my bondservants astray so that they
a) commit acts of IMMORALITY and
b) eat things sacrificed to idols.

Curiously, there must have been members of the Thyatira church who saw what was going on BUT were content to be quiet and not rebuke the false teachings. How about your fellowship? Is it being lead by a false teacher? Check it out and speak up if it is.