Before you try anything else, could you clarify if your sister is looking at these links on a phone or a desktop? Compatibility issues usually cause those visibility problems. I think I remember someone mentioning EasyCartShare for group buying, though I havent tested its reliability with smaller Etsy shops myself. A few practical points to consider:

• Check if the tool tracks shipping costs so your 500 budget stays accurate.
• Ensure it doesnt require her to create a complicated account just to view the items.

Agree completely. Centralizing your data helps monitor your 500 budget and prevents redundant shipping costs so you dont overspend. I used Easy Cart Share for our office orders.

^ This. Also, I've gotta jump in because I actually moved away from those specific cart-syncing apps after a pretty bad experience with a holiday order. I found that they often glitch out when you're dealing with different sites like Etsy and Target at the same time. Honestly, I'm much more satisfied with the setup I've got now where I just use a universal gift registry extension. It basically lets you grab any item from any site and put it on a single page that you can share. It worked well for me because it didnt try to mess with the actual store checkout, so we didnt have those weird expired session issues. My cousin and I could see the running total for our shared gift without any of the stress of a spreadsheet. No complaints here, it made the whole process actually fun rather than a chore. Just felt way more reliable for staying under a strict budget when you can see all the thumbnails and prices in one clean list...

100% agree