First issue is the financial assets. I am not sure if that is all liquid but it is a bit too low. It would be better if it was closer to 15K Canadian. What is your purpose of visit. Your niece’s birthday was not a strong reason? Have you traveled abroad to a country similar to Canada that requires a visa like Australia? How long has your sister been in Canada? Is she established? Does your job provide a good income? Having a job is a good tie to your home country and so is a husband if he remains at hone. Do you have property in your name? Do you care for parents or in-laws? How long a visit did you ask for?
I would consider ordering GCMS notes for more in depth explanation of why you were refused.