I own a condo on the second floor of a three-floor building. The owner of the unit on the top floor wants to install a new kitchen and requires additional water pipes be installed from the basement to her unit, and she asked me if she could run them through my closet but I told her no. She now claims that I said yes. Is this just her word against mine?

Well, to begin with, a condominium consists of common areas and unit. The common areas generally are behind the walls of your unit, i.e. the structural members of the building. Usually electrical and plumbing are within the walls. There is generally also a provision that in the event that any of the common elements such as plumbing or electrical run through a unit, that the unit which has the benefit of the utilities has an easement to continue to maintain those elements for the benefit of their unit. So, for instance, if there was a pipe that ran through your closet when you bought your unit, the unit owner who has benefited from the pipe would probably have an easement under the terms of the condominium documents to continue to maintain the pipe. However, you own the inside of your unit and if there is no pipe currently inside the closet, then the other unit owner does not have the right to have that pipe run through your unit into her unit. With real estate, there is a concept called the statute of frauds (which appears to be fitting in the situation) which requires that any interest in real estate must be in writing. Moreover, when it comes to an easement, which is what the right to maintain the water pipe would be, it not only must be in writing but it must be recorded at the registry of deeds in order to be binding on third parties who do not have actual knowledge of those rights. So you can feel secure that the unit owner above does not have any right to run a pipe through your closet and also, even if she claims that you agreed to do so at some point, that would be unenforceable since there is no writing which would be required in order for her to in fact have a legally enforceable right.