The job of the police is to take reports of possible crimes and investigate. It is the job of the DA to prosecute citizens if the investigative reports of the police suggest that such should occur.
Therefore, there is no law that would stop her from making any report of harassment, etc. to the police or alleging that what you did was criminal. Presumably, the police looked at what you posted and at least thought there was enough to investigate further. Not a good fact pattern from your point of view.
If you do get charged with any crime, you retain counsel (or ask for public defender) and defend at that point.
Now, if she has requested a restraining order (RO) against you, that is a different issue. Obviously, I cannot see what you posted, but a judge probably will and, I am guessing that she will get her RO. The evidence needed for an RO is considerably less than that needed to convict you of a crime.
My advice to you is this. If the relationship is over, it's over. Don't stoke the fires afterwards. Nothing good ever comes of from such "stoking" as you have apparently found out the hard way.
Consult local counsel.