Would have proof of her ties to her home country like job(employment contract and approved leave) and home (rental contract, key money, etc.), proof of savings and return ticket should be enough proof if ever questioned. I would keep a copy of these documents in her phone in case asked to show any proof. You mention needing to save before applying. You are able to apply on your own so if you are saving before a consultant or lawyer is charging you multiple thousands of dollars you can avoid this cost and only have to pay the governent fees if you have the time to dedicate to applying. Many are under the false impression that consultants and lawyers increase chances of approval or are necessary. If a more complex application then a lawyer may be something to consider but if fairly straightforward and from a country like Japan then I would consider looking into the application process to see if you could apply without a consultant or lawyer. Another option is to fill out the application on your own and have a lawyer or consultant review your application before submitting the application which should also cost a lot less. In a straightforward applications you are essentially paying for the time used to complete the application not a lot of skill needed. If you have spent time in person during your relationship and have visiting each other multiple time at least there is minimal benefit to securing PR in Canada so there isn’t concern about immigration fraud like there is from some other countries for example.