It will cost her time and money to file. More than she paid you.
If you are confident that you have fulfilled your obligations, cease all communication, do not respond again at all, then let the chips fall where they may.
If she does file, just arrived prepared, calm, and collected. You'll be fine.
She will not be able to explain her damages when you have emails saying she is happy.
By the way, unless you have not fulfilled your contracted services, written or not, then she has no damages. If she has no damages and sues you anyway, that is actionable by you.
And if she posts incorrect misleading or slanderous posts online, and you can demonstrate that, you can bring a civil action for slander per se. That is very hard to defend against, as the only defense is that what she wrote is true. That action by you has no relationship to her filing anything.
So, if you are up for it, get copies of her slanders, if any, from her FB page. Or anywhere else. Then you sue first, with a better cause of action.
By the by I am not an attorney. I just happen to have unwanted experience and a brother who is a litigator, as in trial attorney.
It is nothing like TV. And just about everything you get here is wrong or imaginary.
Best tip: only hire a firm which has trial attorneys in the practice who know the judge you will be appearing before Otherwise, sure, you'll get an attorney, but s/he may know zero about court reality, which may waste your money. And just so you know, local magistrates are elected, which means not only do they not have to have litigation experience, they might not even be attorneys.
That cuts both ways. So, let her sue. Her odds are poor.