monsters said:
Currently we are living together which is about more than 1 year. 1 year and 2 months exact.
You have no choice. You are considered common-law, and so you must declare her on your current application. If you do not, you will never be able to sponsor her, even if you later marry her.
You were common-law partners as soon as you lived together for 12 consecutive months. It sounds like you were not common-law when you applied, so you did not commit misrepresentation then, However, you are common-law now, and have not landed yet. CIC wants to know when your status changes and when your family composition changes: this includes becoming common-law. When you land, the border agent will ask if your family composition has changed. If you say 'no' and therefore land as single, you will be committing misrepresentation.
You have to tell the visa office that you have become common-law, and want to add your partner to your application. Tell them now. Yes, this will delay things, as your partner will have to have a medical, get background checks, etc., and you will have to submit new forms. However, if you do not declare her now, you will not be able to sponsor her later.
If she has a severe medical condition, this might lead to her being refused a PR, and thus you would be refused too. Same if she had some criminal or security problem. However, in most cases adding a partner to your application will not cause a refusal. You should know already if she has some problem that will prevent her from immigrating.