Even if two individuals were cloned exactly the same, a typical drug would still react differently because of the way it would be administered or prescribed and if two individuals were the same, the composition and attitude of those two would always be different. I have learned and researched the effect of loss or toxic stress on ones life to impair or limit the health recovery in ones body because of attitudes and emotions and anxieties as a result of circumstances that are ongoing and certainly for your Mom, your Father was that circumstance that may have triggered the tumor marker to react. But be assured tumor markers go up and go down with change of attitude and less toxic stress on the persons mind, thereby allowing the mind to help heal the body. This is proven fact. As a matter of fact, sometimes these side effects may be a result of emotions that one experiences due to loss or may be a combination of both.
Loss is always, always an event that is stressful for loved ones, especially family.
When these events or circumstances occur, somehow we need to dig down deeper and try to overcome, because the one that we lost, would not want to be the cause of our decline in health, as I don't believe that would be Gods will either. That is accomplished by reading such very meaningful books as the Dr. Bernie Siegels books or Carl Simontons books and so many others, but one at a time. These tend to begin to bring us Hope initially. WE then get her active in the things that she loves to do, to be around, to keep her busy so that her mind is therapeutically acting to love of and purpose of living. It takes time and patience on yours and hers will and dedication.