HI, thanks for using healthcare magic
It is understandable to be concerned regarding this problem because as you would know, fluids are essential for body function.
If she can tolerate solid food well with no problems, it may be difficult to understand why liquids are problematic.
Though it is definitely possible that they are affecting her, our reactions to food or drink is often influenced by how we feel about them.
For example if we dislike a food or drink , often the very idea of eating or drinking it can make us feel sick. The food/drink itself does not cause the
nausea but our dislike of the particular food/drink inspires that reaction.
Since health is a state of physical, emotional,mental, social, spiritual well being, you may want to consider the other aspects of health.
Her perceptions, ideas related to the consequences of using liquids may need to be explored since physical causes have been ruled by extensive testing.
I hope this helps