Maybe they will ask... why were we started collecting evidence so early?
Don't make it look like you are manufacturing evidence. If you have a relationship, there will be evidence. Some people don't have enough because they didn't keep it, but others are pack rats and do have everything. I think if the evidence is legitimate, the visa officer won't be able to accuse you of some type of fraud just because you collected it; anyway, the VO won't know when you collected evidence.
Examples of evidence that was considered suspicious by the VO or at appeal: a sudden change in the amount of contact - for example, only a few phone calls or emails a month before the PR app was rejected, and then hundreds a month afterwards, to make it look good for the appeal; photos that look staged - one way around that is to try to include some candid photos, where it looks like the two of you did not even realize you were being photographed, maybe in the background at a party or something like that; the applicant not being able to identify people in the submitted photos at the interview; anything that you write yourselves can be questioned - for example, emails, messages, letters, and cards could just be made up - but it is usually accepted at face value.
Or bring up the fact that I only stayed here in Philippines after 8 months so that I can sponsor her.
And it's true....if I was able to sponsor her now I'd go home next week!
Don't stress that you are doing this, though if she is asked directly in the interview, don't lie about it either. Stress that you love each other and want to stay together, but you ran out of money and are going back to Canada to get a job so you can be together as soon as possible.
Is it common for people to apply almost exactly 1 year of cohabiting, the absolute minimum time required?
Some people have.
How should we deal with the question in an interview if they start accusing us of a "convenience partnership"
If the VO asks questions like this, your partner must stress that you love each other very much. Some VOs ask the same thing over and over, trying to make the applicant slip up and admit that the relationship is fake. She should just try to remain calm and reiterate that she loves you and the relationship is genuine.
If you submit a lot of evidence that the relationship is genuine, the interview will most likely be easier.
One thing the VOs do look for as a sign that the relationship is genuine is the attitude to any children brought into the relationship. So include proof that you have a close relationship with her child in the application, if you do. If you don't, try to start developing one now - just taking an interest in the child is enough, if he/she lives far away.