Now I agree that this level of thirst is abnormal and it will be what is causing her urinary signs as well. So, the proin won't have much of a chance here since its meant to help prevent leakage from urinary sphincter weakening not an over production of urine as we have here.
Now if her liver values are climbing this tells us that the liver isn't working as it should. Which can cause both signs we are seeing. So we'd want her vet to be treating this even if the scan didn't show a tumor or obvious change. Therefore that would be something to ring them about here for her.
Otherwise, you may need to double check that the full panel ( or have them do so now) did test her kidney values, rule out metabolic disease (diabetes, Cushings,Addison's, etc), and made sure her calcium levels are normal (sometimes seen with some cancers but also could cause these signs). But again seeing those liver values doubling is a sign that this is likely causing these signs and is an issue that needs treating.
Please take care,
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