K.Z.
I like the idea of making a milkshake in the blender, I presume it is with real berries, which would provide more fiber. You could add other fruits like ripe banana if you think she'd be willing to try a slightly different flavor. Start with just a little bit of banana (or whatever--peach, blueberry, applesauce) if you think she needs to get used to the additional flavor. The extra fruit will provide more fiber. If you think she wouldn't object, you could add oat bran and /or ground flax seeds, or maybe some almond butter mixed in.
I must confess I am not sure we need as much milk as the dairy industry suggests. Maybe her body is trying to say it doesn't like milk, and the only way she can get it down is to flavor it? food for thought....
K. Z.