Originally posted by: badmouse
She's your sister, and she's going to be your sister for a long, long time. Do something that feels right to you so that you won't ever think about it with bad feelings.
Come up with a sum of money that has special meaning to the both of you. For example, the price of a bicycle that you had that she really wanted. Or something like "here's one dollar for every time I told you that you were an idiot - $5219" Or "remember that stuffed bunny I had that you always wanted? It's available on ebay for $150 - here's the money"
The idea is to come up with something really special to the two of you, and tie the money to that.