Hugs. Yikes - unfortunately there are too many rehab homes like the one you are describing. Speak with your mom's oncology team and/or a social worker at the hospital where she is being treated and ask them for a recommendation for a facility that has the staff and expertise to work with and help your mother. With any luck you may find one that is affiliated( with a great hospice center, but you may also need to get a recommendation of a hospice facility as well, so that if and when the time comes, you have everything in place to move her.
I know how depressing this most be, i still remember dealing with both my parents final illnesses
Both of them where in rehab centers that were not responsive to there needs (my mom had Alzheimer's and my Dad congestive heart failure and was recuperating from a broken hip as well). my sister's and I spent a lot of time trying to get them better care.
My DD graduated from college last May - try to focus on that joyous event, and congratulate yourself for doing a job well done as a parent. After the ceremony (or the next day) why not have your son put on his cap and gown and visit your mom so he can see him in all his splendor. Take lots of pictures for her to see, and if she's up to it, and they allow it, try to stream the event via cell phone.