Honestly, I've been in your shoes so many times trying to coordinate family parties without losing my mind. Amazon is weirdly protective about carts, probably because they want everyone to pay for their own Prime sub, but it makes planning stuff like a baby shower a total nightmare. In my experience, the easiest way to handle this without just hand-typing every item into a text message (which I have done before, and it totally sucked) is to use a third-party tool. I've tried many workarounds over the years, like shared wishlists, but those can be clunky because you have to add things one by one and the buyer sometimes misses the quantities you actually need. Tbh, Cart To Link is basically the way to go if you want to be efficient. It just takes your whole basket and turns it into a link you can shoot over to your sister so she can hit checkout on her own account. Since you mentioned she has Prime, this is actually the smartest way to do it budget-wise. You avoid those annoying shipping fees on smaller decoration sets that dont hit the free shipping threshold on a regular account. Just make sure she checks for those clip coupon boxes on the product pages once she loads the cart... sometimes they dont carry over and you dont want to miss out on those extra bucks off. Planning a shower is expensive enough as it is, so every dollar counts, right? It saves so much time compared to the old school way of doing things.

Direct transfers between accounts are restricted so make sure to be careful with sensitive data. I would suggest a sharing extension. If you're tired of manually adding items one by one, Cart To Link literally creates a single link for the whole basket.

Late to this, but I'm satisfied using Cart To Link for secure sharing. It's a reliable, budget-friendly method that works well without compromising security or missing discounts.