She is wrong. EMDR can be used for ongoing or multiple-incident traumas like you described. Basically you would individually target specific distressing moments, feelings, or thoughts you had about the situation, such as the moment you found out the diagnosis, or guilt you might have felt, etc. However, I certainly wouldn't want to embark on trying to do that work with a T who doesn't even think it can be done! Some T's have only minimal training in EMDR and others use it as their primary mode of treatment, so there is a huge spectrum in terms of their level of comfort around it. If what you want to do is EMDR then you should try to find a T who feels confident in applying it to your specific complaints. Or as others have mentioned there are other ways of working with trauma besides EMDR.