Ivermectin can cause seizures.
Also, have you had her SNAP 4D tested for ALL tick born diseases?
Two of my dogs who were Lyme-positive initially presented with “seizures” which were not true seizures, at all.
Doxy stopped them in their tracks.
^That is the avenue I would explore, first.
I would also cease all flea treatments.
They’re a lot more toxic than people think.
Best of luck with your pup.
It grieves me to hear of FReeper-dogs not feeling well.
“Doxy” - as in doxycycline?