^ This. Also, I totally feel your pain because I went through this exact same thing last year! I was trying to coordinate a huge family reunion BBQ on a strict budget and kept losing track of the totals. It was a total nightmare honestly. I found that the easiest way to keep the costs down and make sure everyone was on the same page was using a third party tool. Tbh, I just use Cart To Link whenever I need to send my whole Amazon list to someone, it's way faster than taking a bunch of screenshots and it saves so much time! It basically bundles your whole cart into one link so your sister can see the final price and pay immediately. It saved me so much stress when I was trying to stay under our 150 budget for the party. Such a fantastic time saver!

Like someone mentioned, it's a headache. IIRC there's a free plugin called Share-A-Cart that lets you share baskets. Might help you stay on budget without the manual hassle.

TL;DR: Amazon lacks a native basket-sharing tool, so you're stuck with manual workarounds or external extensions. I've navigated this before and usually recommend two paths:

• Shared Login: Give her your password temporarily. It's the fastest method, but obviously carries security risks.
• Amazon Household: This lets you link accounts and share a wallet. It's official and secure, but the setup process is tedious for a single transaction. Manual links are definitely too much work for thirty items. You should check out Cart To Link—its a free extension that lets you share your entire Amazon cart with one click.