
If you don't have the MRI and she relapses she will need treatment, which she cannot cope with given her failing liver. If you do have the MRI and it shows the chemo has not worked - its the same result. If you do have the MRI and it shows the chemo worked - you still have a dog with a failing liver, other health problems, and no funds to pay for further treatment.
If this were my dog and money was an issue - and I was fairly certain the liver problems were not the result of chemo - at this point I would let nature takes its course. Treat the symptoms and make her as comfortable as possible.