
It all depends what she is allergic too, saliva, dander or hair, and also type of hair.
For example I have a breed with a thick double coat that sheds. A lady had a pup from me 13 years ago as she realised when visiting relatives in Norway with the breed that they didn't affect her as she assumed they would, but she cannot be near short coated or oily breeds.
She visited me while I had two Border Terriers (wiry coats) and they did not affect her at all, yet she cannot be near something like a Labrador, Boxer or Whippet.
The only way to know is to spend time with various coat types, and also be aware that puppy coats can cause a reaction where the adult coats do not.
also there can be an initial reaction to a new dog, but this lessens as the person becomes accustomed/desensitised to them.