Spouse behavior. Husband has inoperable grade 4 glioblastoma

Our 50 year-old son who lives eight hours from us has been diagnosed with grade 4 inoperable glioblastoma. He's starting his third week of chemo/radiation. His wife decided to go camping along with their 13-year-old son to "getaway". She will return for two days and then go take what was a plan of vacation for all of them without him. Fortunately our daughter is with him now and we will go be with him next week. Admittedly his wife has had a difficult time having lost a brother to suicide and both parents within the last two years. We know she is grieving and struggling on her own but somehow I can't get my head around the fact that she is choosing to work 20 hour days, some of it needed to make ends meet, but rather than getting a day away every now and then she's choosing to leave him completely alone. Including not being with him for his upcoming oncology appointment. I'm struggling to find the balance. I understand she is still grieving from losing her father less than a year ago, but somehow I cannot understand how she would take him and her son and just leave him with a sibling. Can someone help me make sense of this?