Unfortunately, pancreatic cancer is an insidious disease that often has no symptoms. By the time it begins to exhibit symptoms and is diagnosed, it is usually variably fatal within 12 to 18 months, if that long. If your aunt has recently been diagnosed with pancreatic cancer, she doesn't want you saying anything to her that will remind her that she's going to die soon -- she already knows that. Talk to her and treat her the same way as you would normally do, for as long as you can..
It's best to save your "goodbyes" to her until she's on her death bed. Then, say what's in your heart. That's when she's going to need to hear your assurances that you love her and that you're never going to forget her.