I think time off to mourn a beloved pet is reasonable. For those folks who don't have pets, well, too bad for you.

I had a wonderful boss many many years ago who gave me a week with pay (unbeknownst to others) to mourn the death of John Lennon. My dad was in the hospital at the same time, so it was a double whammy for me. My dad wanted me with him because he felt my pain and wanted company. I also "paid her back" by being the highest producer that year (and 5 years after) so it made her look good too. She and I have kept in touch occasionally. Funny how you bond with certain people instantly.
I was so lucky and extremely grateful. I know, I know "teacher's pet"