The mass protrusion maybe indirectly related to the lymphoma, but there are many other causes of mass protrusion from the vagina which are possibly related to older age,
urinary problems etc... Knowing when «it's time» is hard since as a loving owner you are biased towards looking at the positives rather than the negatives and since dogs are generally stoic by nature you may not see the full extent of her pain; you really need to look at Precious objectively and decide if she is the same dog or if there is something
different, behavioural changes are usually the first signs.