Oh okay I see ^^
Honestly I don't know much about this kind of trouble, but I guess that until she finds a way to fix her wifi antenna or update through ctr transfer, the card won't work properly (assuming sky 3ds is a linker that was released after 10-11+ firmware versions as far as I remember.
So her 3ds is a stock one huh ? I guess that except messing around finding compatible exploit which used to work with a9lh, that are typically known for being unstable btw, if she cannot fix her antenna or buy a new one, she's basically out of luck.
Hopefully other people could bring their knowledge here too, so we can solve it all together
(Btw IMO fixing her wifi antenna is more important for me than getting the card to work, as system update will probably solve this anyway and she won't struggle to update at each update
Edit : I just remembered that a usb router adapter
used to be sold as an alternative to wifi solutions on Nintendo DS, and I'm pretty sure that a 3DS version
also came out a while ago, so why not looking for this ? If she doesn't care about wireless stuff at all she could use this as an alternative to fix her antenna, which could result in breaking/bricking the console if she does something wrong during the process.