Sadly, NO dog is hypoallergenic per se. Poodles and other such dogs shed less and so their dander doesn't "get around" as much.
Dander comes from the animal's saliva, not their hair. Even Chinese Cresteds and Mexican Hairless (Xolo) dogs are not "hypoallergenic".
Trust me, as a person with allergies I have researched this. It is best for your grandmother to visit the breed (be it poodle or maltese or whatever) before making that kind of decision. The good news is that dogs generally have less dander than cats so if your grandmother is allergic to cats she may be fine with dogs. :wink:
Good luck!