Two seems obvious but not for her. Three is what she likes. When she has some finger food, pretzels or cookie chunks, she wants one in each hand and one in her mouth. When she plays with her rings or we go outside and play with Johnders' tennis balls she has to have three. No matter how awkward, she must have three. She will let you hold an item while she readjusts the other two but she will manage to get three as quickly as possible.
The ancients were on to something and it is verified by the randomness of my daughter.