Good questions and thanks for asking for our help, this is why we are here. Yes, preliminary research is just that and can be lengthy depending on what the project is pursuing. I am a little unsure of how I can help you, but I will do my best. First what is the question you are trying to answer (i.e. what are you trying to find out)?
The length of research is not uncommon to be about 3-5 pages for a student at her grade level, and adequate background research is necessary to determine the hypothesis. But, you should check with her teacher on the length on the research project and how much involvement you should expect to put into it. The way you described her research, sounds right on point. However, you shouldn't need to perform an experiment BEFORE you come up with a hypothesis, there should be enough information out there to determine an "Estimated Guess"/ hypothesis on your own.
Information on forming your background research:http://www.sciencebuddies.org/science-f ... plan.shtml
Here is more information about forming a hypothesis, http://www.sciencebuddies.org/science-f ... hypothesis
(you form it based on the research you have done to find additional information you interested in finding out, which it sounds like you have nailed it:
janet_425 wrote: "I think the craters in Oxia Palus and Mare Australe will be the deepest for their width because..."
. To complete that sentence, you could say something like "these craters will be the deepest based on the research I have done studying moon crater width." It is an educated guess (based on your 3 page background research, and tells your guess that those craters will be the deepest in comparison to others).
This may offer an example similar to what you are trying to accomplish:http://www.sciencebuddies.org/science-f ... background
Have you checked out NASA resources?http://www.nasa.gov/mission_pages/MRO/n ... 90924.html
Hope that helps. Let us know if we can assist further or if anything was unclear.