You would be completely in the right to ask her not to wear perfume since it's your business. Most businesses will have a sign that states something like, out of consideration for others, please do not wear perfume...or you can mention allergies.
A lot of people are sensitive to perfume, so I'm sure you're not the only one that is bothered by it. It may just be easier for them to stand it, if they are in and out of there.