Honestly? This is not a very nice response, its PA, but what I would do is torture her subtly.
Ok lets look at the facts: Ex cheated on his pregnant wife with CF. He then left CF for half a year to be back with the mother of his baby. Then he went back to CF.
CF has got to know he's a slimy guy, and be a bit wary of "other women" especially you. After all he was with you first and he went back to you at one point, and you are still the mother of his first born son.
So now here she is, not really conveying information, just confirming information you already established with Ex. So I would subtly feed into her suspicions and insecurities about it. Every time she confirms a time you already know, smile slyly (yes I know, its text she can't see it, but I firmly believe if you own a feeling it comes across) and reply back "well yes, when Ex and I had our check in discussion we confirmed this weekend's times and few other upcoming dates" or "so this hasn't changed since Ex and I got together to discuss arrangements?" and all sorts of other PA comments that let her know she's not required in this transaction, you and Ex have worked it out together, just the two of you, as a parental team, and she's not involved in the planning.
If she wants to make digs, don't get hit with dirt - pick up a bigger shovel.