My mom just had to have her Miniature Pinscher euthanized on Sunday what can i say to comfort her?

She had her for 13 years now and the dogs health had been deteriorating for the past 2 years. She started having heart problems and couldn't hardly see anymore. I'm an only child. Lacey was like a second daughter to her. She had been to the vet off and on the past 2 years and they did everything they could until it was no longer manageable. My mom wants to have her cremated so she can spread the ashes in Lacey's favorite spot in her backyard. My mom is very depressed now and sad like she lost a human child. I know it will get better as time goes on but i really don't know what else to say. Everything i've said has not helped. Should i suggest that she join a pet loss grief support group?Please help this is no joke! Thank you!