My sister did the same thing to me, she made some excuse about it being because i was supposed to do something for her daughter, my niece and i didnt.. Its not that i do not want to do it its that its not time to do it yet, and i need funds. £300 is not a lot of money, trust me i burn that fast. Although i plan on surprising them in Jan 2021. I know that something very serious happened and i was accused for doing something i didnt do. It caused a rift between me and my sister, because of her daughter. I still love them unconditionally and care about them.

Just show love for your sibling if you surprise her by being thoughtful and caring and concerned even when she doesnt deserve it, what will that say about you. She is family and will always be, so keep caring about her.