As long as she carries proof there is no problem
Carry all medicines in a separate bag and declare it at security as what it is,
Do not allow any medication to be carried in the hold, it all must be in cabin baggage
If she is traveling on her own, inform the airline at check in and the crew on boarding, this is just in case a hypo occurs the crew knows what it could be.
Plenty of spares in case of loss or breakages
Copies of prescriptions or empty boxes of medication so it can be replaced if needed
Under no circumstances order Diabetic meals as these are designed for Type 2 sufferers and do not have enough carbohydrates for Type !s
Carry additional foods like biscuits etc. in case of delays
Enjoy