It could possibly due to Migraine as the previous poster said, migraines do cause some scary symptoms and I have been known to faint when Im having a especially bad migraine. But it may also be the Singulair. Im taking Singulair myself but it isnt working for me. I would read the inclosed leaflet of her Singulair medication and see if fainting is a side effect. If it is, see the doctor and stop the medication and try something else.

Also oxygen levels will go down during an unconscious episode. Have the doctor check her oxygen saturation levels.

I havent heard of a bleeding valve as being normal. Personally I dont believe that is normal. I would have this investigated also and if treatment is needed, it should stop the fainting episodes and make her feel a lot better. Take care.