I just spoke more to my mother who said that the vet made the point of pointing out Layla's concave sternum. The official diagnosis was "severe pectus excavadum." Mom thinks he was planning on putting her to sleep today, but when he saw her tear up changed it to "let's take it week to week." Since the vet visit, mom said she has not been active and seems to be having more and more trouble with her breathing every hour. Once she reaches the point (if there is one) of appearing uncomfortable she will have her euthanized. Unfortunately, she doesn't think she can bear to be there, so I have offered to take in and have DH bury her when the time comes. At this point, we'd really rather her die with my mother. Luckily mom has this week and next off for vacation, so she will be around when she passes.
I have shed so many tears this afternoon. When she was born, she wasn't breathing and Ruby tried to kill her (she went for her neck immediately), but we got her breathing and she has lived for 8.5 weeks. Now I wish we'd let nature take its course, but at the same time I know she had known love for 8 weeks. I don't know which is better... *sigh*