I want to thank you for letting that child into your heart, I think it's wonderful. My story might help you to understand why. I'll try to make it brief and try not to confuse you.
I was 20 when I had my first dd15. I met a man when she was a year old and his parents welcomed her into their family. They would give her birthday presents, christmas presents and always treated her and I with the utmost respect.
This man and I never married (and aren't together anymore) but we ended up having DD12. Never were either of my DD's treated any differently, their bio-granddaughter and my daughter were the same in their eyes. They still come to see her and still to this day give DD15 gifts. They are the most wonderful people ever.
Fast forward to now, I am married to a wonderful man and we have DS7. He treats my daughters as if they are his own. His mother is another story. The sun rises and sets on my son for her. But my daughters she could do without. It is very sad and my daughters notice. She didn't even recognize their birthdays this year. No Christmas presents either. She makes my daughters feel like they are less than their brother and it has made my relationship with her nonexistent. My DH has spoken to her and she refuses to change. She has had 9 years to get used to the idea of my daughters.
It is more than the gifts, they don't need the gifts, I would be happy if she showed my girls an ounce of respect.
So for whatever time that child is in your life, make sure they feel loved and special, it's all a child ever wants.