No one knows, of course, what was going on in your aunt's mind; she may not have known herself. After all, our motives aren't always obvious, even to ourselves. The Psalmist said, "Who can discern their own errors? Forgive my hidden faults" (Psalm 19:12).
I can't help but wonder, however, if her reaction was caused (at least in part) by a combination of guilt and regret. As your aunt looked back, she may have realized that their lives could have been happier if she had only tried harder. If so, she may have felt guilty over the past, and hoped somehow that a lavish funeral might make up for it (although it wouldn't).
It also may have been a way to express regret for all the years that are now lost and can never be recovered. In addition, since your uncle's death was sudden, she may feel an extra burden of regret because she had no opportunity to say she was sorry or express love.
Don't be too harsh on your aunt; whatever happened in the past, she's lonely now and needs your love and compassion. More than that, she needs to discover the depth of God's love for her, and open her heart and life to all that Christ can do for her. Ask God to help you and others in your family reach out to your aunt with Christ's mercy and love. And treasure the family God has given you, so you'll never look back with guilt or regret.