Is drug therapy the way to get Mom over the grief of losing her beloved dog?

We moved my mother and her poodle of 9 co-dependent years to an assisted living facility two months ago. One month ago we had to put her dog to sleep rather suddenly. She never went anywhere without him, including church every week! Mom is 81, and has middle stage dementia. She has no other health problems, but now she is fixated on mourning the loss of her dog. She carries his ashes in a lovely little purse most places with a cute stuffed dog. I understand this need but would love some ideas on how to help her mourn. The facility says it is hard to know how to make her happy under these circumstances. She calls me constantly wondering about why he died, is he cold, he shouldn't have had to die etc... Heaven is just a bit too abstract for her now. Do you think Zoloft would be a good thing to try short term. She has always been pretty sensitive to medications, but the doctor recommended this as a short term helper. My mom has been a happy person all her life basically and folks love being around her because of her JOY!! I live an hour away with kids I homeschool and this is quite difficult. Any ideas??