Answer: There are so many hostas that could match that description somewhat, it would be better to match the plant in real life with another one to be certain of having a pair. There are thousands of different hostas and a description or even a photo does not make identification reliable. Hosta "Christmas Tree" is variable green edged in white so I doubt that is it, and Hosta "Night Before Christmas" has variable leaves with a white center and green edge but not as narrow as you described. "Silver Kabitan" has a predominantly white leaf with a green edge but it is a very small plant and is not listed in the Monrovia on line listing. There are also occasional leaves that grow white spontaneously and are not representative of the cultivar. In my experience, if you want an exact match, you might consider dividing the one you have into two. That is probably the easiest way to get another one without some trial and error. I'm sorry I can't be more specific for you.
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