You could try that
It would probably be a good idea to mix it at first anyways just to do a gradual transition,that way it doesn't cause stomach upset.
If she continues to eat only certain parts even with Harry Hamster if you use the tough love method(basically leave food and don't refill the bowl until everything has been eaten,but make sure these aren't shells of seeds or nuts!)it might be necessary to use pellets,but in most cases it just isn't an issue with hamsters if dealt with in certain ways.