The Halti I am assuming is what we call a "gentle leader".... it is the halter that goes over their nose and around the back of their ears right?

Like Aly said, the key is getting her used to it. She should understand that it's a good thing. Try putting it on her for about 10 minutes at a time while in the house. Pet her and give her a treat while she is wearing it. Do this a couple times each day until you think she is comfortable with it. Positive reinforcement will really help her get used to the halti.

I hope this helps! !