Abandon pet dog for self interest?

A woman called me up three weeks ago to ask me to walk her 13 year old Shih Tzu-Terrier dog.  From what she had told me - in bits and pieces, and that I did not want to be too intrusive -   when I visited her and the dog, this dog was brought in by her daughter 13 years ago.

This woman's husband passed away 4 months ago, and she said she has been, and still is, depressed. In addition to that, she is not physically well. The daughter is still around with them, and she has a maid. She said that the daughter is too busy to care for the dog, and that the maid, being a Muslim, is reluctant to walk the dog. The dog is still active with lots of energy. If she had not mentioned his age, I would not think he was over 10 years of age.

During that visit, she dropped some hints of sending the dog away. Hopefully, she can find a person to adopt it, and not sent it to the shelter. She added that he was a burden to her. I told her that since she is not giving her any problems -he does not eliminate in the house unless taken out and bark - why not let him spend his remaining days with her. Besides, she needs the companionship. I suspect she did not buy into both of the reasons.

I got back home and wondered why is she asking me to still bath and walk the dog when she has decided to send him away. My friend mentioned that maybe she felt guilty, and wanted to treat him well before departing.

I went to walk and bath the dog for the first time 2 weeks ago. A few days after that, she called me to come over for a second visit, and added that she had brought the dog to the vet, and that he has arthritis and dry skin problem. She mentioned again she has to send it away, and if there are no takers, she will put it to sleep. Again, I persuaded her not to do so. her reply was: "He is living in my house, so I will make the final decision..."

After my second session with the dog last week, she told me her friend "wants to try him out". If it does not work out, she will put him to sleep.  Later that day, via sms, I suggested she also advertise him over the internet. Her curt response surprised me: "Why not you do it. We are all very exhausted here".
It has been a few days since we got in touch with each other. I don't want to find out the current situation either.

The reason I am writing this is to reflect how easy it was for her to - harshly put it - dispose her dog.   If the dog is sickly or incapacitated, and it would do the dog good if it were to be put down, I agree with the decision.

I wonder how many more owners easily give up their pets. Dogs in particular. I read somewhere that the top three reasons owners abandon their dogs are: aggressiveness, excessive barking, and destruction to the house. Maybe depression does cause one to take necessary actions to alleviate the intensity.