It sounds like it might be a fibroid, which can cause continuous bleeding if it is near the cervix.
At the least, be sure she takes dietary iron or a supplement every day.
I think you do need to get her to a doctor if she cannot stop bleeding. But possibly being certain she takes an iron supplement or eats a high iron diet will work temporarily to keep her from becoming anemic from all the bleeding.
I think this kind of bleeding can happen for different reasons. One of them is an overproduction of the hormone progesterone. So she has periods and then heavy spotting between the periods. My own mom had this and took prescribed hormones to balance it out. If she didn't take it, she'd start bleeding. If she has a polyp or fibroid, that also can cause continuous bleeding. Thyroid issues can do a number on your period because hormones are affected. Since it happened before and she took medicine to make it stop, likely it is the same cause. Cancer can cause abnormal bleeding for sure but I'd think it is because of other issues. Happen to know the medicine she took last year?
In my area, doctors are doing virtual medicine at the very least for patients. You all still need care. She needs to call the doctor she had last time or another to discuss this. She could become anemic bleeding so much (lack of iron). That could be the feeling she is having of blood pressure dropping as fatigue is a symptom of that. Please call her doctor. Let us know what happens, try to do it all virtually and if you call the doctor that treated her before, they may try the medicine that worked before to see if it may help this time too. Let us know!