I think she’ll leave 2018 up to PDJT, and re-appear when the 2020 campaign starts. She made a few appearances for 2016 presidential election and probably will do the same next time.
The way she’s treated by the Rats/MSM is despicable, and they’ll be enjoying the company of each other in Hell. I hope it’s worth it to them.
And if FLOTUS did attend? The press would angle the reporting to the negative anyway. POTUS is working it until the midterms and needs to keep up a brisk pace. If FLOTUS needs to concentrate on the homefront, let it be. It is THEIR prerogative.