The brands PLouise, Made by Mitchell and bPerfect are very fashionable at the minute and all 3 are often featured on Tiktok. They all have really great nude palettes and lots of offers atm. I just bought my niece a PLouise palette normally costing £40 for just £25 and got 2 other products free.
You haven’t said what age your sister is but if she’s a teenager I think Dior or Charlotte Tilbury would be too old for her. My teenage nieces are all into bPerfect and PLouise. Huda beauty and BeautyBay have some great palettes too.