There is no need to write to IRCC. It is fine for her to travel to Canada with you on her TRV. There is no worry about "mismatch", misrepresentation or this affecting her PR in any way. Life circumstances change all of the time.If she writes to CIC regarding change in circumstances, Does it carry the probability of getting her TRV cancelled?
I can run with a number of things:
1) She can visit her brother for a month in October and return back only to come back again in Feb.
2) While she's visiting, I can marry her. Again, this looks suspicious.
My only concern is getting her here ASAP after marriage and ensuring a smooth PR sponsorship process.
She will be entering as a visitor, so she needs to have a return ticket. Tell the truth, that she is visiting you while applying for sponsorship. Don't volunteer extra information. Have proof of finances. I also suggest you pay the full PR fees ahead of time and try to complete some of the app and have that with you.