Surprise gift vs planned gift?

My sis needs a phone replacement as the iphone she’s using is 5 years old and practically falling apart.

She can’t afford to replace it or get it fixed because the current prices are just absurdly high.

I’m planning on gifting her the new 18 series iphone. But I have no idea what colour to get or what model. Whether the pro or pro max, and what spec.

Does it make sense to just transfer the money for it and ask her to buy one herself? I did that for my mom last time. And she took a whole year before actually buying a new phone😑

So I’m thinking if I should just buy it and surprise gift it. But again, what if I get the wrong model or color🫠

Which is better?