Yes, your dream could actually mean something... let's see what it might mean
We start at a house. A house usually stands symbol for the dreamer's state of being: physical, mental, emotional, communication, privacy etc... And it normally stays true even if it's not your actual house, but somebody else's house, including a dream somebody else. And the dream concentrates on the state of the basement. The basement is something underneath the house, hidden, so it points to your unconscious, but also instincts. You know from the start that what is going on there is a bit out of the ordinary... you do no happen on it by chance, but visit it backed up with a whole team of helpers/aids who know a bit about the strange, the 'abnormal', the psychic, the paranormal, etc... Your fear too shares that you're apprehensive of what lives in your unconscious.
In the unconscious lives a 5 year old child. Children often symbolize an innocent part of you, but in this case the innocence has become corrupted. The child is possessed, and it being possessed might mean this part of your unconscious feels helpless and not in control. You mention it growls at you and speaks in a voice not hers. I wonder whether she spoke in tongues too? Did you ever make out what she actually tried to say to you? Is it possible that she asked for your help, and that you never understood that message? When you start to run away from her out of fear (a translation of your feelings of helplesness), then you do not give the help she may have been requesting from you. So, from that point of view her running after you is even very understandable. Spraying her with water could be seen as you trying to clean her from the possession. But if we look at possession as just a symbol of helplesness, then spraying water will hardly be helpful. Plus it adds a sense of rejection of the helpless innocent part of you (which it basically remains, possessed by a demon or not). If you rejected a helpless part of yourself wanting you to help it then isn't it understandable it got mad?
However, the fetching of the priest and doing an exorcism is an act of coming back with help. You do not run away from her, but you leave with the plan to return and get rid of the feeling of helplesness. And an exorcism's possible meanings is exactly that: taking control of things again. And so, the dream ends, because you finally managed to do what the dream wanted you to solve: solve these unconscious feelings of helplesness and regain control.
Hope this explenation may settle your anxiety about the dream's memory
