Blackouts, has anyone experienced them?

Hi, my sister was diagnosed with fibromyalgia a few months ago. Just over 2 weeks ago she began blacking out in an evening, normally about 7/7:30 pm. These blackouts last from about 20 seconds up to about 5 minutes, and the episode as whole last about an hour and a half. While she is unconscious she can still feel and hear just not respond and when she comes round again she can carry on a conversation. During the shorter ones she also stops breathing, but is able to breath during the longer ones. This has happened while she has been in hospital as well and they have check her pulse/blood pressure/blood sugar ect and all have been within normal rates. About a week ago these began to happen whenever she ate anything, and the episodes vary in length and intensity depending on the size of meal she eats. A big meal results a longer episode, a small meal causes only a small one, however she will still have one in the evening. I was wondering if anyone has every heard of anything like this, or has any more information on it.

Thank you.