Love hasn't got anything to do with money. As the Beetles said ; 'Money can't buy you love' - and children know when they are loved. Find things to do with your granddaughter that her other grandparents do not do, not as competition, but so that she has things she does, places she goes, that are special to each of you.
Whenever my 15 year old grandson comes to stay I still read him a bedtime story. It is the same book every time, a pop-up book about a haunted house that belonged to his father when he was small, now it is a bit of a joke, but I do the voices and he acts scared. This is special between us and hasn't cost me a penny.
Perhaps you can teach her to sew, or to cook, or foster a love of flowers or insects, or always go for a walk to the park.
Just spend time with her, listen to her, talk to her and soon your relationship will be special for what you can do with her