Did they check her blood sugar levels? You may try giving Nutrical or Nutristat just to make sugar it isn't hypoglycemia or even Corn syrup if that is all you have. Has she been exposed to ant or bug poisons, fertilizers, new plants, any new flea or tick treatments. My mom's dog was having seizures and only showed up as kidney problems. It turned out to be ant poison exposure. Although Lucy's seizures are short, it sounds like her recovery from them is much longer than normal.
You said they did an MRI so that would probably rule out brain tumor and probably the link I am giving you, if they looked at her pancreas. Prayers for Lucy I hope the anti-seizure meds start working.
Pancreatic Cancer (Insulinoma) in Dogs | petMD