Generally this is not a symptoms of that.
You can actually read the symptoms of Hiatal Hernia here as well.
read here
I don't know what type of doctors she has seen. But a Gastroenterologist would be best to determine what is going on. Also, has she had her sugar checked etc? You may want to have her put some crackers next to her bed and eat them before she even get out of bed, with resting about 15 min after to see if this helps at all.
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