If the RRIF is designated to go to her estate, it is distributed according to her will. If she designates you as the beneficiary for the RRIFs, either in the RRIF documents or in her will, the RRIF(s)so designated can pass tax free to you as her spouse. If she designates anyone else as the beneficiary, that RRIF is deemed to have been deregistered and is taxed as part of the estate. The assets of that RRIF pass to and become taxable assets in the hands of the named beneficiary.
A TFSA is slightly different in that it can only pass tax free to the TFSA of the spouse if the spouse is designated as the Successor Holder for that TFSA account. If the spouse or anyone else is designated simply as the beneficiary of the TFSA, the account loses its tax free status as of the instant of death.