Yes, she could be allergic to a yorkie. All dogs have dander which is usually the culprit of allergies (this is coming from a severe allergic person, who's now on meds, lol).
The allergic reaction to small dogs and dogs with thin coats as opposed to thick double coats is that the dander is minimized, and the allergies are less. But in a severly allergic person, the amount of dander doesn't matter and anything will bother them.
Also, dog coats are notorious for bring in outside allergins such as pollen, mold, ect. That can be troublesome for people with allergies as well even if the dander isn't an issue.
What I do to help, is I have air purifiers in every room and I use a liquid called ALLERPET on my dogs after bathtime... this further strips the dander off of their coats and can be used as many times a week as needed without harming the dog
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