It can be scary when our Mom isn't feeling well. A person can faint or "fall out" from many different reasons. Just be glad that she went to the hospital and they will take good care of her.
Sometimes it's because the person didn't eat enough food or ate something too sweet.
Sometimes it's because they have a very bad pain that they can't stand it.
Other times it's because their blood pressure is too low or two high.
There are too many reasons to list on here. I just hope that your Mom will be okay.
Please let us know how she is doing. Meanwhile, try not to worry too much - they will take good care of her in the hospital.
Wishing you the best