How sweet of you to help your grandmother. My grandmother was one of the most important people in my life and I love to see the younger generations honoring the "Wise Ones". Good luck on your search.
Ultimate Box is also an excellent brand of card writer. It and some others have also added software that allows resizing and splitting platterns. It works with HUS, PES, and PCS. I am not sure about other formats. I have the Ultimate Box and it is an excellent product.
First, and most important, does your Grandmother have a rewritable memory card? If she doesn't have one, there is no way to get the designs to the machine. So, she would need to get one, along with the writing device (such as a Magic Box or Amazing Box). Then, it is a simple matter of transfering the designs (temporarily) from the computer onto the rewritable card. Mine can only hold 6 designs at a time, but I believe there are newer versions that can hold more than that. There isn't a way to add them permanantly to the machine's memory.
Have you tried to contact the machine dealer? They will be best able to help you resolve this (and any other) problem with the machine. If I remember correctly, the Rose is made by Husqvarna. That means it will use the .HUS format, so it will be best to save all designs in that format, if possible. You can convert from other formats, but that is just one more thing to do, and after too many conversions data may be lost and the design will become corrupt.
great info, thank you!