Fortniet skin bundel?

I would like to have the wildcat fortnite skin but don't want to buy a new switch for me, but my aunt has had nh switches for a long time and my question is whether I can get the skin trz even though my aunt has an old switch

No, you can't, you can buy a code (which still costs at least 90 euro). You can then redeem this on the older switch.