J.G.
I'd give her a good 24 hours or longer after finishing the meds before giving her milk again. I always use the 24 hour rule.
Also - I think watered down milk might make ME throw up. Yuck. Too watery. Wait a while, then give her what she's used to. Also - give her smaller doses. Not sure how much she drank, but you said she finished her cup. Maybe it was too much, too soon, too weird-tasting.