Because these episodes are short lived, you maybe able to provide some reassurance by listening to what specifically is scaring her, and trying to alleviate that situation in a safe way. Remember - its as real to her as your reality is to you. Is someone breaking into the house? Tell her and show her you're locking all the doors and windows. Someones watching her through the television? Throw a blanket over it.
I wouldn't suggest being this indulgent if these were long term or continuous hallucinations, but for a temporary fix it might help. Also, if possible, see if you can discover anything that seems to directly trigger them: a sound, a word, a colour, a food, a car light on the wall, could be any number of things.
Because your own health scare has exacerbated her symptoms, be sure to inform and include her in all the things you are doing to be healthy. Explain your medicines, doctor visits, diet, etc. If she feels calmer about your health, the attacks might decrease in frequency.
Thanks for sharing, and for bravely helping your daughter.