So very sorry this wee one is going thru this! And you too! How scary
.
If you can, be sure to get the foaming and/or the "seizure" activity on video - it's soooo helpful for a Vet to be able to see what you're seeing/describing.
When she gets vaccines again - I'd for sure use Benadryl about 30-45min prior, even though this may not be vax related.