That is one role. Another role that I have is as a scientist. I sometimes make intellectual contributions to class members' research projects, but to date I have not documented these contributions through identifiable authorship. My conflict is in supporting you in the best way that I can and encouraging you to take ownership of a research project, but at the same time appropriately receiving my own credit for intellectual contributions to the research. Perhaps the acid test is whether or not your project looks considerably different than it would otherwise because of comments or suggestions that I have offered.
Authorship is a hot issue.
In some cases, your project has always been completely your own intellectual efforts. In other cases, substantial contributions may have been made by the instructor, although you were always the primary investigator. Do what you think is appropriate. I truly defer to your judgement without prejudice.