Sorry for your loss. Pension splitting can be performed in the year of death, however, it is a pro-rated calculation based upon the date of death. In your case, nine months apply and this should be able to be completed without performing any overrides using TurboTax Online or Download/Installed in your computer.
I'm going to suggest contacting our Customer Support team for assistance with this. Here's how to contact them:
https://turbotax.community.intuit.ca/replies/3152013
