I would test on her cows milk on things like her cereal. Does she eat yoghurt and eat things you cook with cows milk?
The other thing you can get are those tetra packs of S26 so it's ready made and easy to take travelling. Most formula's are cows milk based I think???? So if she is on a formula already, I think it would be ok to taste test her on the odd cup of milk.
Keep up the the formula and also try the cows milk before you leave. Then if she is ok with the cows milk here you will be ok.
Hope that makes sense, I seem to be rambling