welcome to healthcare magic.
The most common cause of blood in vomiting
is gastric ulcer,swelling of GI tract or swollen veins due to liver damage
Let the blood report come to lighten the picture.Then you might need other tests.
Does she have any gastric problems earlier?Does she smoke or take alcohol?What color was the blood? (Bright red or like coffee grounds?)Any medicine she used tio take?
Wish her good health.