Your duty is not to manufacture feelings, but to see to those who need your support. If you spend a day at their house cooking meals for their freezer, teaching the kids things they don’t know how to do, and being there to provide what they need in terms of emotional support, that would go much farther than filling hankies on behalf of your own sorrow. There is nothing wrong with the latter, mind you, but it is often the former that is more needed, and longer remembered with fondness.
Besides, if you were to change places with her, you would be grateful if she would help out the family you left behind, and you would think her of greater merit if she did so without regards to whether or not she felt a great affection for you. The blessed, after all, are concerned for the living, not themselves. The care of her loved ones would be her fondest wish. Mind that, and don’t worry that your own feelings are holding up.