I am very sorry about the loss of your aunt. Unfortunately, you do need answers and the only place that can give you these answers is the hospital. I believe you would have to be next of kin to her to be able to request her full medical record and you can consult with a malpractice lawyer to help you understand what you are reading, if nothing else. I am not telling you to sue the hospital, since there may have been appropriate tests ran and nothing detected. However you might need some help reading a medical record and they may be the ones to help you with that.
Best of luck and take care,