ailibaba,
are you coming back to Canada in a few days? Have you prepared all your documentation?
yes, in their eyes, your ticket would be one-way, but personally I don't think having a return ticket in YOUR case would help much. Just get yourself prepared with all the needed documents and if they find out you have an inland app in progress, ensure to have all what might be requested to convince the IO that you will leave Canada if your application is refused. Showing past employer's reference letters, any kinds of recommendation letters, proof of family ties, bank account with sufficient funds, all qualifications, proof of the ongoing relationship with your partner while you are away from her/him etc, that's what I would do if I leave Canada...being too prepared always is better than not enough.
Good luck!