Honestly, it is baffling that Amazon still hasnt added a native share button for carts in 2024. Over the years ive run into this same wall dozens of times while trying to coordinate big group events or office orders, and honestly, the wishlist workaround is a total waste of time because of the quantity issue you mentioned. In my experience, the only real way to handle this without losing your mind is to use a third-party tool like Share-A-Cart. Its a simple browser extension that solves exactly what you are dealing with right now. I have used it for everything from wedding planning to coordinating party supplies like you are doing for your sisters event in Chicago. Basically, you just click a button while looking at your cart and it generates a unique link. When your roommate opens that link, it populates their cart with everything you picked out, quantities and all. I have tried many other methods like exporting lists or the screenshot route, but those are just too prone to human error. This is much more direct and ensures the total is accurate for both of you. It is honestly the most practical fix until Amazon decides to catch up with how people actually shop nowadays. Just send her the link and you are done.

Quickly jumping in here since I just dealt with this for my cousin's wedding last summer. Being super paranoid about browser extensions and giving anything access to my accounts, it took me forever to find a safe way to do this. I eventually settled on using Share-A-Cart. It is basically a Chrome extension that generates a specific code for your items. This felt better because it doesnt actually ask for your Amazon login or password, which was a huge dealbreaker for me. You just click create cart code and send that random string of numbers to your roommate. She puts it into their site and it just dumps everything into her cart with the right quantities. It worked reliably for our 40-item order, though it can be a little slow if you have a ton of stuff. Just make sure you both have the same delivery region set or the prices might flip out. Tbh it is the only way I have found that actually keeps the counts right.

I am satisfied using this Amazon cart sharer tool.

• Extension: Free, maintains quantity metadata.
• Manual list: Free, doesnt capture counts... Accurate data transfer works well for coordinating tbh.